You know, I bet Konami is getting really tired of quashing Metal Gear Solid 4 rumors at this point. The PR team would probably throw a gala event if the game were ever announced for the 360, simply to celebrate the fact that everybody would finally be shutting up about. Konami PR's Michael Shelling, who I am sure would look amazing in a tailored tux, responded to our own inquiries with the following:
"For the record, Metal Gear Solid 4: Guns of the Patriots is a PlayStation 3 exclusive and there are no plans to develop an Xbox 360 version of the game."
That is straight from Konami by name from a direct inquiry from Kotaku. End of story.