The speed at which MS pulled 'Flight' gives some indication as to the returns they expect from games software development these days.
A flight simulator on the PC platform will never bring that kind of return. So they tested the water with Flight, they reviewed, analysed and made their decisions.
I am also quite sure that the license sale to Lockheed will have included some conditions:
they arent allowed to enter the games, consumer market for instance.
But dont read into this that MS is planning to return to this market.
Its just a standard 'rights reserving' thing to do.
I think that the future for flight simulators lies elsewhere now.
Yes, one may invest in PRD but in the end that product will develop further and further away from FSX.
FSX is the end of the line as such.
MS wont return to this market.
It just wouldnt make any commercial sense.