For Aristotle, the very reality of the potential or possible is posterior to the act, so much so that, among temporal beings, if there never will be an actual X then X is impossible. “Never to be actualized possibility” is, for him, an oxymoron.
This would seem to be provable. All possibilities are possibilities for some term, but this term just is the act. Again, if a possibility is for a term, this term is either itself possible or actual. If possible, then this repeats ad infinitum. Therefore actual. To allow for this actuality, we have to posit something not limited to time, for example, an idea or a scientific law. I’ve called it elsewhere an intentional field.
Actuality gives reality to possibility, but it does not do so by existing first in time, but by giving structure to the process of development in time. Actuality is thus not merely temporal (for it does not pre-exist in time) nor outside of time (for it is to be actual in time) but trans-temporal. So far as something is limited to time it is possibility of one sort or another.
Thus, time as such is, on Aristotle’s account of it, a potency without an act. We refine this to mean time so far as it limits things to time.
(Time, considered in Einstein’s block universe, is not the whole of actuality, but only actuality as limited to time. The transtemporal structure – which includes the scientific law if law is law is real – is not captured in the block.)
Here we have a purely ontological sense of omne quod movetur ab alio movetur. Changes involve possibilities, but these are ontologically dependent on transtemporal actualities.
Time itself on Aristotle’s account is a source of corruption. The sense – unexplained by him – might be that corruption occurs to the extent that the actuality can no longer dominate or control the merely temporal possibility.