I'm coming around to the new Bruce Banner, because I do like Ruffalo and I'm sure he'll do a good job, but I'm still bitter.

My theory about not bringing Edward Norton back is because he and Joss would have gotten on like oil and water. Joss likes to have strict control over what's going on, Norton's known for taking charge so things work his way. I don't think it would have worked, so it was mutually agreed that Norton bow out.

(That's actually my second theory. My first was he and RDJ wouldn't have gotten on, but the more I think about it, the more I think it's the second).