'statements about future events can't have a truth value until they occur'
'what'll happen will happen'
Presentism best describes your first statement; and your second statement appears to be, not a form of fatalism but a tautology.
Presentism is the view that only the present is real. Contrast this
doctrine with eternalism, the view that past and future times are
just as real as the present time. Or, past or future individuals are
just as real as present individuals. They just happen to exist prior
to the present, or after the present. One might compare presentism
with actualism in the metaphysics of modality. Actualism is the view
that the actual world enjoys a special ontological status over other
worlds, if other worlds there be. Only the actual world is instantiated, or in some sense real. The presentist wants to say the same
thing about times: Only the present time is real, and the present time
enjoys a special ontological status over other times, if other times
there are. (Matthew Davidson, 'Presentism and the Non-Present', Philosophical Studies: An International Journal for Philosophy in the Analytic
Tradition, Vol. 113, No. 1 (Mar., 2003), pp. 77-92 : 77.)
On a presentist approach, no statement about the future can be true because there is nothing it can be true of - or false about. If the future (like the past) is non-existent then it contains no truth-makers (events, states of affairs) that could make any present truth-bearer (a sentence, statement or proposition) true.
This supports : 'statements about future events can't have a truth value until they occur'.
'What will happen will happen'
I take this to be a tautology. It is true by virtue of its logical form irrespective of its content.
This is not fatalism. Fatalism can take many forms. One of these is logical fatalism, which can be introduced roughly as follows. Note that the argument does not assume presentism.
Consider the following argument: first, assume that it is
presently t2, and that the past tense proposition, 'At t1 it
was the case that at t3 Susan will go to Anstruther', is true. Since
this proposition is about the past, and since the past is necessary
(given that it is impossible for any true proposition about the past
to be false henceforth), the proposition is necessary as well. But
the proposition also entails the truth of the future tense
proposition, 'Susan will go to Anstruther at t3', in which case
the latter proposition is also necessary. Therefore, it is now
necessary that Susan will go to Anstruther in the future, and thus
she is not free to do as she wishes.
The preceding type of argument - call it the argument from
temporal necessity (or Type I) is often thought to pose a real
threat to the non-fixity of the future. At least, it is meant to give
us more cause for concern than the other most common logical
fatalistic argument type the one from antecedent truth value (or
Type II). Whereas Type I has it that past truth about the future
fixes the future; Type II has it that present truth about the future
fixes the future. So, according to the standard interpretation of
Type II, the logical fatalist infers the necessity (at, say, t2) of
'Susan will go to Anstruther at t3', merely from the trivial
necessity of the following conditional: 'If it is true, now, to say
that Susan will go to Anstruther at t3, then Susan will, indeed, go
to Anstruther at t3. But it is a notorious modal fallacy to infer p from (p ⊃ p), as this interpretation implies the fatalist has
done. The Type I logical fatalist, however, infers p from (q ⊃ p) where q is a past tense proposition which entails the
future tense proposition p. It is the concept of temporal necessity
that allows the logical fatalist to make this valid modal inference. (Joseph Diekemper, 'Temporal Necessity and Logical Fatalism', Proceedings of the Aristotelian Society, New Series, Vol. 104 (2004), pp. 289-296 : 289-90.)
Logical fatalism is not determinism
Logical fatalism depends purely on implications within tensed modal logic. Determinism depends on causation - here, on present conditions (events, states of affairs) being causally sufficient for future conditions. Causation is irrelevant to logical fatalism.