I can see MS having more of an entertainment box, but no way have they built up their 1st party (lacking I know, but still there) and continue to do so (4 new studios in 2011, plus expansions) to exit in a couple of years.
especially as by the time the next xbox launches, they'd have made $2 -$3+Bill on the 360 ecosystem.
And the only way Sony would leave is if they went bankrupt.







