I can't say I wouldn't buy it if it's P2P, because I pay for xbox live. I just hope it's less than $50 a year. For $50 a year I get a huge friends list, free downloads occassionally, play any Xbox 360 console game with my friends on that list, and... well I guess that's about it.
I'll be a little angry, but still buy it and pay for the online play. That having been said, they better have better servers than the original Starcraft on Battle net had, and better make more effort to stop map hacking, because that pisses off micro-oriented people like myself.
The biggest question, though, isn't whether I'll pay to play online. The big question is will the other millions of people buying the game pay for online play or even buy the game if they have to pay for online play?
When it comes out I'll be looking forward to playing on Battle net with you guys. It'll be meeting some of you for the first time, but if you like Starcraft, then we definitely share a common interest.