I'll give my thought on all of this.
When I first read the news, I stared open-mouthed at the screen for about a minute as I read. While I've learned not to take what George Lucas says to heart, I honestly believed that there would never be another live-action film, at least during Lucas's lifetime.
Once my shock subsided enough, I began to think about what this sequel trilogy would be like. I'll admit it, I'm optimistic. Disney owning it doesn't bother me, (I won't be surprised if they end up owning everything one day), since many other Disney-owned projects have turned out great (Tron: Legacy, Pirates of the Caribbean, Pixar, etc. And since the major downfall of the PT was Lucas's poor directing and creative choices, there's a possibility of the new films being the films we wanted with the prequels but never got. There's also the possibility that they could end up being worse, but I truly think it's a bad idea to make assumptions about something before we have any details about it.
As other people have mentioned, there's the possibility that we could get the OOT in good quality. Disney wants to make money, as much as they can, and I'm sure they know there's a demand for the originals to be properly remastered. Lucas refuses to release them because he doesn't consider them the true versions, not because of any money issues. Disney could care less.
I'm keeping an open mind. If this is a Godsend, that's great. If not, oh well, it's not the end of the world.