"For the record," you can't really believe what Konami of America's PR says. They are IN NO WAY allowed to confirm a 360 version until, well, Konami of Japan strategically decide to announce it, and they definitely want the Sony ver to do well and not be affected by rumors of a 360 port.
KoA might not even be aware of KoJ porting it, really.
This is the same as RE4, DMC4, VF5, PSP games that eventually get ported to console, etc. "Oh no, it's exclusive." There's definitely plenty of reason to believe MGS4 will come to 360 in the future, and speculation and rumors will continue until months after the Sony release.