how the hell will they fit a game thats ment to be using the whole 50gb on blu ray onto a dvd9?
The fit 5 games onto one with The Orange Box or all of Mass Effect on one.
Blu-Ray has limitations which have been mentioned on several games such as Lair, Resistance and Oblivion with data being repeated on disc, multiple usages of textures (the same textures being duplicated per level as opposed to one file) because of read speeds etc... Where as DVD9 doesn't have this problem.
It's possible they could use a couple of discs if needed too.

, the only thing for certain at this time is that it is a ps3 release, has been built from the ground up for the ps3 and not one member of kojima productions nor konami have ever stated that there is a 360 version planned or in production.