Well according to the book, Ezra dies but the makers of PLL stated that the show isn't following the book. Therefore, we can assume Ezra is still alive. As for A, well my suspects are Jason, Mrs.Dilaurentis, & maybe some who knows Melissa, someone whom we are not paying attention to. Cause if you look back to the finale, in the police station Melissa said something to her father about Spencer not killing Ali, in other words Melissa knows who A is.
CeCe, I don't think she's A, she's blackmailing about Ali being alive because she thinks Ali blew up her cover but we all know its A. And A can not blow up he/her own cover, can they now?
That's my theory for the A case.
-Sanaya