The graphics in the video on Microsofts website are looking very near to FSX graphics. Of course there is a difference with aircraft shadow and visibility of the landscape. But runway, trees, cockpit ... it all looks like the graphics of FSX. Maybe Microsoft Flight will provide a new core engine, but with the same way of using 3d objects, textures and so on.

Webisode 2 http://www.microsoft.com/games/flight/

... Microsoft should make it FSX-addon-compatible . If not, it would be another stupid Microsoft-decision, like not really use multiple cores in FSX.