Well, the fact about the "expanding to Blu-Ray" piques my interest.
Tied in with "CliffyB being a major X-Box fanboy"...
This narrows my speculation to 3 options:
1.) GeoW3 goes on PS3 for the sake of making a 50gb (or maybe at that point, 100gb) game on a Blu-Ray disc.
2.) Fanboyism and brand loyalty take over, keeping the franchise on 360. GeoW3, being only a 9gb game due to its extreme technical limits at that point in time, would get destroyed by competition.
3.) PS360 game. Everybody wins. Well, GeoW1 & Geow2 fans would be the losers because they lost their exclusivity, and they would get a massively gimped version (9gb
So basically, by the time Gears 3 comes out, the new X-Box better be ready so Microsoft can still stand a chance. But me, being a Sony fanboy, says, "Fuck you Micro$oft. And Epic, give me my Gears 3 while the damned 360 dies with no predecessor to leave behind."