The funny thing that noone seems to have noticed is that FSX was sold off to LM shortly after MS killed it. Selling it off to someone who was willing to invest in it, is after all a sound business decision. Just dive into P3D and look at the content, such as the "Load flight" dialog, and compare this (as well as the graphics, enumerations, etc) to FSX, and you will understand.
On the funny side, P3D is definately worth checking out if you can, and I'd say it's indeed a real candidate to supersede FSX if simulation is what you're into.