Theological question about something I read in a part of the Talmud

I’m not Jewish in an ethnic or religious sense but I have tried to read some decent amount about Judaism out of some interest. I am not sure how much of this question is still applicable to Reform Judaism but this is purely theological and I am just asking out of curiosity anyways.

I can’t say my understanding of more traditional(or even Reform) Judaism is great so if you see any misconceptions here that’s why.

Something I thought was interesting is in the Talmud under Yevamot 62a. “For R. Assi49 stated: The Son of David50 will not come before all the souls in Guf51 will have been disposed of, “.

So my understanding is that according to the Talmud the Treasury of Souls contains all the souls that will exist, and these souls must be born and die before the Son of David comes.

What, then, theoretically happens if man becomes extinct before all of the souls can be born and die i.e there is nobody to give the souls life?