Though the class is full at USC, I believe there are some people with multiple offers and maybe some holding multiple seats. I have recently seen some posts like "USC vs. Creighton", "USC vs. UNLV", and "USC vs. Loma Linda". Based on that, I'm guessing some more seats will open up.
If the adcom meets once a month and then releases some seats (like they did Mar. 6 and Apr. 3), maybe there will be some more activity in early May. This is just my best guess. I really don't know how that all works, so maybe seats will open up sooner (or later).
I'm waiting on USC too. Good luck to us! Also, good luck to you with NYU. I hope you get the one you want.