Marx's economic determinism includes an element of teleology, rooted in his conception of human nature. You ask whether Marx's view of history is solely about what has come into being; or, whether it is about what may come into being; or, whether it is about what must come into being?
It is not solely about what has come into being. Marx is not interested in history for its own sake; he thinks history offers more than a mere chronicle. Nor does he rest his political programme and his analysis of economics and society on what merely 'may' (or may not) come into being, a roulette wheel view of history. I think he does believe that his predictive science of history is about what in some sense must come about. Marx does not think he can 'time' future events - date the future advent of socialism and communism. But he does think that there is an inherent, non-accidental tendency for the productive forces to increase and for that increase to produce the revolutionary changes he predicts. We may decide that 'an inherent, non-accidental tendency' is a rather soft form of determinism. But I am content to count the inherent and non-accidental as (without too much strain on the term) determinist.
There is much dispute about the precise form of Marx's economic determinism. Marx is widely regarded (when his determinism is not denied altogether) as a technological determinist, with technological change seen as the motor of history. I do not need to take sides in this controversy. I settle for the view that for Marx there are two fundamental factors whose interaction - vitally including their tension - is the major key to historical change. These are the forces of production and the relations of production. The forces of production are roughly land, capital, and labour; the relations of production are patterns of ownership.
As these stand at a period of history, they form the economic base or structure of society to which the superstructure - the state, law, morals, religion - is functional. This is clear from the famous passage in the Preface to the Critique of Political Economy:
In the social production of their existence, men inevitably enter into definite relations, which are independent of their will, namely relations of production appropriate to a given stage in the development of their material forces of production. The
totality of these relations of production constitutes the economic structure of society, the real foundation, on which arises a legal and political superstructure and to
which correspond definite forms of social consciousness. ... At a certain stage of
development, the material productive forces of society come into conflict with the
existing relations of production. . . From forms of development of the productive
forces these relations turn into their fetters. Then begins an era of social revolution.
The changes in the economic foundation lead sooner or later to the transformation
of the whole immense superstructure. (Marx, A Contribution to the Critique of Political Economy (London, 1971), 20-21.)
As the forces of production change, wholly or in part due to new technology, so the patterns of ownership change, and the superstructure alters to accommodate the new situation. In a celebrated quote :
Social relations are closely bound up with productive forces. In acquiring new productive
forces men change their mode of production; and in changing their mode of production, in
changing the way of earning their living, they change all their social relations. The hand-mill
gives you society with the feudal lord; the steam-mill, society with the industrial capitalist. (Marx, Collected Works, Moscow, 1975, VI: 166.)
Teleology, productive forces and human nature
Although Marx identifies some nomological correspondences -- for example,
that feudal economic arrangements are incompatible with a world of factories and machines - which in themselves do not single out either the
forces or relations as primary, he believes that there are crucial respects in
which the development of the productive forces constitutes the (relatively)
independent explanatory variable. His commitment to the thesis of the determination of the relations of production by the productive forces lies at
the center of his historical vision; this development unifies history and
explains its basic contour.
Does this imply that the productive forces have a certain developmental
autonomy? The correct answer here is a firm yes and no. On the one hand,
any improvements in the productive forces, whether in labor skills or tools,
take place within the framework of not only a definite set of production
relations but of a whole social context, and thus the productive forces
cannot be said to advance in an independent or self-contained fashion.
Indeed, Marx acknowledges the existence of societies in which a virtual
stagnation of the productive forces had been brought about. On the other
hand, Marx does have a conception of human nature in which man is seen
as inherently expanding (or having a propensity to expand) his capacities,
and so it could be said that the productive forces have a natural tendency to
advance. The production and reproduction of material life is the basic
function of society; but unlike other animals, man does not rest content
with a given mode of subsistence. The cycle of production is not stationary. As man produces, as he utilizes his own productive abilities and manipulates the world around him, his powers tend to increase. Nor should
it be surprising that the productive forces have a propensity to expand,
given the incremental nature of human knowledge and skill, and the relative permanence of the means of production. For Marx, human production
itself seems almost intrinsically to involve, an expansion of productive
capacity, and he sees the relations of production as generally changing only
in response to the possibilities opened up by man's improving productive
forces. (William H. Shaw, '"The Handmill Gives You the Feudal Lord": Marx's Technological Determinism', History and Theory, Vol. 18, No. 2 (May, 1979), pp. 155-176; 164-5.)
Teleology and the end of capitalism
There are further elements of teleology in Marx, though I can allude to them only briefly. Marx believes that the situation under capitalism is marked by the exploitation and alienation of labour. He also believes that the proletariat, laborers who own no forces of production, will come to realise their situation and also that it is remediable by social and political revolution.
It will be evident, he thinks, that socialism (characterised by public ownership and the principle, 'to each according to his work') will present itself as the immediate alternative to capitalism. Socialism, under a technology of abundance and the disappearance of all classes except the proletariat, will yield place to communism and the principle, 'to each according to his needs'. (The non-proletarian classes will not be lethally eliminated; they will simply join the proletariat since there will be no other, ownership-controlling role for them.)
Communism will, Marx believes, provide the conditions to enable the flourishing of creativity in which human nature will find its essential fulfilment. 'Man is a species-being . . .and free conscious activity constitutes the species-character of man' (Marx, Early Writings (Hoare, ed.), New York: Vintage, 1974: 327-8). There will be no more exploitation or alienation or (a bugbear with Marx) division of labour. In the picture sketched in The German Ideology, Marx first describes the constraining nature of work pre-socialism and communism, then sets out the many-sided development of human creativity - of species-being - that communism will ensure :
For as soon as the distribution of labour comes into being, each man has a particular
exclusive sphere of activity which is forced upon him and from which he cannot escape.
He is a hunter, a fisherman, a shepherd or a critical critic, and must remain so if he does
not want to lose his means of livelihood; while in Communist society, where nobody has
one exclusive sphere of activity, but each can become accomplished in any branch he
wishes, society regulates the general production and thus makes it possible for me to do
one thing today and another tomorrow, to hunt in the morning, fish in the afternoon,
rear cattle in the evening, criticise after dinner, just as I have a mind, without ever be
coming hunter, fisherman, shepherd or critic! (Marx, The German Ideology, (Arthur, ed.), New York: International Publishers, 1970; 53.)
Thomas E. Wartenberg, '"Species-Being" and "Human Nature" in Marx', Human Studies, Vol. 5, No. 2 (Apr. - Jun., 1982), pp. 77-95.
Howard Sherman, 'Marx and Determinism', Journal of Economic Issues, Vol. 15, No. 1 (Mar., 1981), pp. 61-71.
William H. Shaw, '"The Handmill Gives You the Feudal Lord": Marx's Technological Determinism', History and Theory, Vol. 18, No. 2 (May, 1979), pp. 155-176.