Well, Capcom isn't on a great financial situation right now. Biohazard is the biggest thing they still hold. Of course, I'd rather have them doing Dragon's Dogma 2 (There's rumors of that!) or a new Dead Rising (that'd be glorious!), but priorities come first.
Resident Evil 6 also has the bonus of offering offline co-op for both campaign and extra modes. Just like 5, that is a great bonus in my eyes, which also made me enjoy the game even more playing it with a buddy. If only Chris' arm didn't take like half of the splitscreen... -_-"
He needs the big arms so he can take revenge on the boulders :P
I think the coop actually ruined RE5. Apart from the fact that Sheva's AI is ridiculously awful, the original footage before idiots started calling the game racist and CAPCOM shoehorned Sheva in to appease people actually looked so much better. Much scarier, more tense, and thicker mobs of enemies. It could have been so much more, which is why it bugs me :/