So sad no linux native, but wine testings?
From what little research i did in 5m, it looks like UE3 works quite well under wine, so i was thinking maybe get a guy from playonlinux or codeweavers crossover to have a go at optimizing it under wine. That way there might be out of the box unofficial linux support at launch!. I bet they will have it up and running in no-time. And since its ue3 a decent newish nvidia card should do fine under wine. I bet all it would take to get the commercial crossover to fully support it is a sticker on the box, and such. Playonlinux is the free alternative to crossover, its quite good aswell. Crossover costs like 30-40 bucks with 1 month support, so its not to bad.
Then there is ubuntu’s software center, im not sure what criteria is required for it, im guessing they will ok a crossover official support, not so sure about playonlinux. Another thing to mention is that linux users are in most cases starving for games on linux, especially new titles, even if they are not running optimally compaired to windows. Most people will rather play at half the framerate if its playable, rather than shut down all the projects they have going and boot into windows for an hour or 2 just to play. If its possible to get close to between 40-60 fps its playable, im guessing that wont be a problem, but im more concerned about keyboard/mouse input and responsiveness, getting a head start on that would basically make the game linux supported. That said i cant wait for this game to come out =).
edit: Also consider that steam beta might be comming before next year, and there might be possibility’s that valve will accept a wine cooperation as acceptable official support. Either directly from wine , playonlinux or codeweavers. That would mean a linux/crossover stamp in steam, along with windows/mac.