Didn't see news of this as of late here but several weeks ago, word has surfaced. Remember a while back, around August, when guests were asked a questionnaire of what attractions they want to see happen, and dislike, etc. Well, it seems the audience has spoken and Universal just might be moving ahead, and talking with James Cameron to replace T2 3-D: Battle Across Time with a Avatar 4D attraction, shooting for a 2014 opening at both Hollywood & Orlando. Which will be the year Avatar 2 will be released.
Sources: Universal Studios Hollywood plans seven new attractions, end of Terminator 2: 3D | Theme Park Tourist / Universal Studios Hollywood