Uh I think you're overstating the number of games coming to OSX. So far it's still pretty much only Valve that's carrying the banner.
Besides, as I illustrated above, these leaked photos (should they be real) all but rule out the possibility of a dedicated GPU. The nature of manufacturing suggests they do not and will not use radically different PCBs within the same model. The GPU cannot be in any other location either (the bottom half of the computer is just the battery cells).
Blizzard has been on since at least the days of Warcraft 2. Oh and EA's starting to make a showing as well.