There are several takes of this throughout the history of philosophy.
One of the earliest examples I can think of is the philosophy of Dilthey/Misch, where the Kantian idea of transcendental [German transzendentale and transcendental also in non-adverbial form, i.e. necessary conditions of the possibility of experience, not the same as transzendente and transcendent in non-adverbial form, i.e. beyond all possible experience] logic is relativized historically, i.e. the factual and embodied knowledge of various times is understood as founded on factual and logical/conceptual conditions of that time. Both can change, which is exactly what makes history possible and actual reality. A related concept evolving around that time and being coined shortly thereafter out of that idea is the hermeneutical circle.
The most famous example is by Michel Foucault, the historical a priori or episteme, as laid out in The Archeology of Knowledge and The Order of Things respectively. It expresses a similar thought to the one of Dilthey/Misch.
What both takes have in common is that epistemologically, they analyse the factual and conceptual historical conditions and show how certain insights have been dependent on them and both necessary for the time and necessarily true only as embedded into that particular historical context.
Coming to the paradox: As I see it, it confuses two aspects that above-mentioned authors are careful to distinguish - historical process [meta-layer and abstract fact] and historical setting [factual situation at a time]. An improvement of the understanding of history does not exactly change the pace or nature of the historical process. A change of the historical setting does, i.e. coming to know more or other "facts" in general. Knowing more about history is but a small aspect of it.
In other words: It is new knowledge that's never been there (or been completely lost) that outdates knowledge, no matter whether historical or not. But historicity of knowledge is a fact that is only epistemologically accessible in hindsight. It is only what already has happened that we can know, i.e. epistemologically accessible. These are the huge insights of Dilthey, Misch, and Foucault [well, and others]. Therefore, saying something about the current state of the process of history at large is indeed paradoxical as it is impossible by the very nature of historicity. All we can say is that everything that is and ever has been (and ever will be) is only real insofar as it is historical.