Of course, students can still get in if they apply later, as long as Pitt still has spaces in the program they are applying to. And they can get merit if they apply up to the merit deadline, as long as Pitt still has merit available.
But from what we heard from the AO, it helps to apply early for the most favorable consideration of your application. Part of the message I got was that if you apply later, your application might need to be relatively stronger to receive the same consideration.