Just finished the last of us, it's pretty amzing. It's a little puzzling why they're only planning one single player DLC though. I hope it's meaty, I want more of this game. Don't deviate from the level of quality you've given so far, really make it count on the DLC. This is a game with a ton of potential stories to tell, I hope there'll be a few, or at leats one that's truly massive.
As for the multiplayer, I hope the infected become involved as map hazards in new modes. If the two ultiplayer dlc were just new maps without any infected at all, that would be disappointing.
I'd love to see some larger maps, a goal of some kind (food, etc) a bunch of infected to worry about when firing or what have you and an enemy team? That would be amazing multplayer match.
Of coop would be nice, towns with much needed supplies, infected, similar to some of the levels in SP. With 4 men, that would be a lot of fun too. A few different types of enemy placement would add a lot to it... still, it'd be more fun with two teams.
Love the game, excited by the possibilities... don't make it a bunch of map packs, Naughty Dog!