Blu-ray would still be used for the games. And how would it be obsolete? Just because Hollywood may not adopt it as the next standard format, doesn't mean Blu-ray would be an obsolete piece of technology.
It won't matter, it's still a format (and a great one at that) for games to be on. 50GB on a DL Blu-Ray disc is still great for games. MGS4 is supposed to take up a whole dual layer BRD