It's doable on the PS3/360, but on what games? Wipeout? Rayman? These aren't demanding games by any stretch of the imagination. You won't see Halo 4, Uncharted, God of War, Gears, etc running at native 1080p.
I agree that games next gen will a shit ton more going on. I just believe that MS and Sony will pack some serious hardware in there to handle it. We'll see.
Edit: To be honest, I know there will still many games outputting in 720p next gen and at 30fps. Frankly I'm still ok with that. 720p looks perfectly on my 60" Aquos when I game, and 30fps is not a problem to me.