I'm amazed at so many of these comments. We complain that there isn't enough happening, then we complain that we don't like when they choose to do something. *sigh*
This move can be categorized very simply. Avatar is a giant brand, and Disney is betting that it's on the same level as their investments in Star Wars and Indiana Jones. There is a huge built in following that represents immediate money making potential. For this reason, it is a significantly better play for Disney than coming out with Beastly Kingdom. Get over it already, if they can take advantage of existing marketing and fan base, they should, and good on them.
As for the fit, well, it's a lush planet with a myriad of interesting wild animals. Sound familiar? Focus on that and you won't have any problem understanding the fit. Giant blue people or not, this one is going to be about the planet and the very unique interesting animals. A dark ride could be great. I imagine something like the Indy ride in DL only with a new ride vehicle, perhaps something more like the Potter ride.
I for one say "Yay!" this is going to be a lot of fun... and if anyone cares to know, I am not a huge Avatar fan, but I see the vast potential of the franchise and the creative expanse it delivers.