I'm looking forward to Left 4 Dead getting additional content - I can't wait for the other two campaigns to have versus mode enabled on them, it seems like something that the game ought to have shipped with really
I'm worried that Valve is going to get overwhelmed though, what with still having class packs for TF2 to make, and people expecting entire new L4D campaigns, on top of rumours of Portal 2... god knows when we'll actually see Episode 3!
Other than that, I will definitely check out Braid and Burnout Paradise when they come out on PC. Other than Trackmania (which is a different beast entirely), Burnout's always been the only racing game I've really enjoyed, so it's good to hear that this one's coming to PC. I've heard that it's rather awesome, too.
Oh, and there's a bunch of DS games I'm looking forward to as well. Castlevania: Order of Ecclesia gets a European release soon-ish, as does Chrono Trigger (which I'm ashamed to admit, I've never played). They've both been out in America for months though, annoyingly - I suppose the delay is mainly for translations, and since DS games aren't region-locked I might just give in and import them. Also I want N+ on DS, but that doesn't appear to be getting a European release at all, so I'll have to import that too (from the Atari online store: "We're Sorry. One of the products you selected has been excluded from purchase in your country.")