Bullshit. MGS4 isn't on the 360....
... yet.
i assume they want to keep the X360 60fps original demo engine that's running on a real gpu quiet for at least 6 months.
In all honesty, I highly doubt they could get this game running at 60 fps on XBOX360. The game could certainly be done on 360 if you ask me, but I do think it might suffer in a way similar to PS3 ports of XBOX360 games. I know the original engine demo was done on a PC, but that doesn't immediately mean it would easily translate to the 360 either.
The 360 and PS3 are pretty close in terms of raw power, I'd estimate. The PS2, however, was significantly weaker than XBOX in most areas (though PS2 certainly has its advantages). MGS2 was a game designed very specifically for PS2 and suffered greatly when ported to the XBOX.
If they were to spent a signficant amount of time redesigning it for 360, however, I'm sure the results would be excellent as they could apply what they had learned creating the PS3 game to this updated engine essentially learning from earlier mistakes. At the very least, the installation screens would be removed.
It would certainly have to ship on multiple discs, but due to the way it's broken up, that would not be a problem in the least. In fact, some might prefer swapping discs to waiting for 2-3 minute install. Have 1 disc per act or something.
I would love to see a 360 version just to see how well someone could port a game designed for PS3 to the 360. It's generally the other way around and we all know how that works. Do you really think they'll do it? I suppose it depends on sales. Despite all of the used copies you're seeing, the original sales numbers remain and Konami has made money on those copies. It basically matched MGS3 and exceeded MGS1 and 2 for first day sales with a much smaller userbase in Japan. I suppose a lot hinges on the US and European sales, however.