Yes, theming will be a big factor obviously, I expect full-on theming, nothing like the blandness of the Soarin' queue. The visuals they can create in a queue based on this movie could be stunning.
And I don't have hat in the ring or really truly care what the sequels do. But I do know James Cameron rarely puts out a big budget dud and they will definitely pump up the promotion for this one to get people reminded of it. They'll remind people of how successful it was, What an amazing visual world it was, How much money it made, etc. I just don't see a movie that made $2.8B not going at least over $1B, possibly $1.5B or higher, mostly from the money they'll make on it's domestic opening weekend and overseas.
The movie may be a pretty mediocre movie, but if it captures that world again and maybe it even is good, then there's no way at least the FIRST sequel fails. After that it's anyones guess, but a movie doesn't make Almost $3B and then just bomb (financially) when a sequel comes out.