I knew about all the other stuff, but I must have missed these. At least now I know the answer to the question that always was in the back of my head. What are they going to do about Prestige Classes?
As for pure vs. multi-classing, it's a personal call in all cases. As a player who hates single class I can say that I will continue to miss out on some of the "best of the best" enhancements, spells, and other things that come with pure class. I am interested in those things, don't get me wrong, but I also don't want to (IMO) throw away 16 perfectly good levels on just pure fighter (for example.) I would say that the things that are introduced would have to be stellar and really, really, really hard to resist for me to make another pure class character again (deleted a 14 cleric just because he was single class.)