grrr said:
Yes it just doesn't seem feasible that a game of this (rumored) size would run on 360 at this point, and your point about the 720 makes perfect sense because that way everyone's happy eventually.
May I point out that it is disputed whether the 360's full potential has actually been used yet. For example, The Escapist ran an article a while back quoting Cliffy B (Gearbox) stating that
"With creative programming you can squeeze anything out of any given platform,"
"Go back to the demo scene where these guys would take a 286 PC and in 38k make a demo that rivaled the most triple-A game of the time."
"It's just a matter of code magic, time and effort...I don't know how much longer the 360 will be around, but I'm sure that if we have a product coming out before the end of [its] lifecycle we'll continue to try and squeeze more water from that stone."
He has a point. Hardware manufacturers cannot predict the full capacity of their own products. As such, I would expect the 360 to have at least five more years as a major console.
http://www.escapistmagazine.com/news/view/114118-We-Can-Still-Do-More-With-Xbox-360-Says-Bleszinski