It's probably Crash, but I'd like to see a few older PS1/PS2 series get rebooted also:

3x3 Eyes
Battle Arena Toshinden
Bloody Roar
Contra
Fighting Force
ONE
The Perfect Weapon
Parasite Eve
Policenauts

Just to name a few...

I doubt it's going to be an unannounced AAA title from a 1st party studio. Those are reserved for the big game conferences. I'm going to guess GTAV for PS4.

Wipeout?!?Shenmue 3!?! Doubt it is Crash. I wont be surprise if it is a multiplatform game.

Activision is sittiing on the Crash IP. Sony needs to expand Naughty Dog and buy the Crash franchise and reboot it. Microsoft just bought Gears so why cant Sony buy Crash?

Wipeout on the ps4 would be pretty awesome looking.
Gta5 is very likely
Crash would be kinda.... meh ish really, his last few games have been so so
Titanfall can't happen because the first game is set in stone exclusive to the X1
Pokemon? because it's more likely than Titanfall
Or.... Monster hunter, would be pretty massive and has been a number of years since there was a proper Monster hunter on the playstation home systems

I do not think Sony needs to buy Crash. Microsoft needed to buy Gears because their studios lack creativity. Also wouldn't it have been better to reveal Crash @ E3 than on some playstation magazine. I do wish it was Crash, but I going keep my expectations at a minimum lol. I would alove to see Onimusha/Colony Wars/Syphon Filte/Wipeout and Shenmue 3.

There are more speculations that it is Shenmue 3.

that actually makes a lot of sense. I wouldn't be surpised if it turns out to be GTA V.