I think everybody here's overlooking one really important fact: It's a challenge for the Academy to find FIVE films a year worthy of Best Picture. Increasing it to ten can ONLY lower expectations of what qualifies as a "Best" Picture.
I mean, take last year. I would argue that The Curious Case of Benjamin Button didn't even deserve to be one of the five nominated. It was good, really good, but not great, and if there had been five more slots to fill, you'd have only gotten five more movies that weren't as good as Button. The same goes for Michael Clayton in '07. Again, good, but not great. If we're going to HAVE standards, let's keep them raised, not the other way around.
Oh, and this decision will have some bearing on animated features only if the oh-so-insulting Best Animated Feature category goes the way of the dodo and animated films are actually allowed to compete with live-action ones again. A great film is a great film; the medium is irrelevant.