Well, so either Tai Lung is not appearing here, or else he would appear and they're just holding out on telling us just to have us speculate whether he could be back or not. Personally? He would be the only reason I'd have for even giving the sequel a chance.
Of course, I would not like seeing him come back in a role like the first one. If he is still alive, he should not be after the Dragon Scroll anymore, if anything he'd want to come back to beat down on Po, but considering all the things going for him that have potential to be explored (the issues with Shifu, Tigress being his adoptive sister, a possible team-up wth Po, etc.), it would be great if Tai Lung returned and joined the good guys to fight the new big bad. If he doesn't come back and it turns out the Wuxi Finger Hold did kill him, then that just turns Po into a smug, cold-blooded killer, meaning that just cements how much I hate him. lol
I guess I can only hope he appears, cause not even the awesome Gary Oldman as the villain would make me watch this movie otherwise.