See, that's what I was thinking that they would do for a sequel. But I wouldn't like that sinceClick to see Spoiler:I liked the human aspect of the movie, how Grace, Jake, and Norm had to fall asleep in that machine in order to take the form of a Na'vi, hence the title "Avatar." They would have to eliminate that, as Jake is pernamently a Na'vi. The only one that would still be able to do this is Norm, but his avatar had been shot (unless his avatar is unaffected). And Grace is dead, so yeah.
Thinking about it, if they do do a sequel, they simply can't call it "Avatar 2", since avatars won't be prominent.