There are still big games coming. In fact they have something as big if not bigger than Assassin's Creed coming this fall from a western third party. But I can't be the one to make that reveal. Hopefully it's mentioned tomorrow.
AssCreed, as a franchise is pretty huge, with 3 selling over 12 million copies. The only 3rd party games that I can think of the top of my head that are as big, if not bigger than it, are COD, GTA, RDR, Battlefield, WoW, Diablo. Whatever the case may be I hope the game is polished and is not a bug fest like AC3: L, I'm almost done with that game and what a mess it is. Still overall enjoyable, but I don't see potential from those developers to make a big jump like AC1-AC2 like I see Bend doing with Uncharted.
EDIT: You are talking about sales being a little lower than AC franchise, so now I have a pretty good idea what you're talking about, depending on the developer is, would be exciting
If the Vita became an indie machine I would pick it up in a heartbeat: FTL, Fez, Braid, Lone Survivor, Hotline Miami, Frozen Synapse, Binding of Isaac, Legend of Grimrock, Limbo, Superbrothers, Defcon, Uplink...
Fuck.
PSM was supposed to be just that, along with many other ipod/android games like fruit ninja, cut the rope, angry birds, etc. Too bad that initiative is a major bust, it had so much potential too.
Well if this is Sony "new strategy" for Vita then it'll need something really popular like DayZ or Minecraft.
DayZ would be awesome. Minecraft, I don't personally care, but can see the importance.
Speaking of PSN/XBL games, Shadow Complex would work great on Vita IMO. EDIT: And Super Meat Boy and Castle Crashers too.
If Sony was smart (they aren't), the majority, if not all, PSN games would be playable on vita.