I think it is quite likely to look crude eventually. It's wonderful now, sure; even my cynical brain enjoyed it, though mostly because of the design rather than the implementation. But given how dodgy lots of older big-CGI films look now, I think in a few years' time we will be saying "yeah it was great then, dated now though, look at how X moves or what the detail on Y is".
I spend a lot of time on Uncanny Valley issues and I can certainly say that Avatar hits a few. There are two things that I think people still don't do properly: firstly, bone/musculature and skin, skin's never proper and what's supposed to be underneath it doesn't help. Skin is not PVC and even very sophisticated skeletons don't properly simulate how fibres and muscles look. To me, they look like rubber still.
Secondly, the animations still aren't as good as they could be - which is an artistic issue, not a technological one. There's a certain sort of overly fluid movement that animated animals have that just feels wrong. You can mocap humans, but for organic things where you can't it's incredibly hard to do - this isn't calling people rubbish, this is very very tricky stuff, but it's still not right.