Unless they also make the patents coming with it public, it would be of no use. As long as I remember, Microsoft has no good history of purchasing patents and making them public. Google has (vp7,vp8, Webm as an evolution). But probably some of the patents are expired anyway.

I also doubt that they would open source the ported version (c# I suppose) but they could do this to the previous Delphi version, they developed many useful components so even without the core functionality, UI code might be useful for Lazarus/Delphi developers