I don't really care about when it is, but when they release track packs I hope they do it via patching (like the Battlefield games do). By which I mean: everyone get's a new version update for the game which includes the new tracks, and in the store you can buy and download an unlock key. If you buy the key you can play on the new tracks in single player / split screen, and you can host and join online games using those tracks. If you don't buy the key then you can still join online games with those tracks, but nothing else. Same with teams: if you buy the key you get to play as the new teams, if you don't then you still get to join games where other people are using them.

Actually, that must be how they'll release it, right? Splitting the online games up into people who have expansions and people who don't would be retarded (think about how many variations there would be with 2 track packs, never mind 3 or more).