From the standpoint of someone working at Microsoft and responsible for the Windows SDK, this is incredible news. We are basically acquiring some of the best tools for that space (low-level, hard-core devs) as well as the services of two very talented people in Mark Russinovich and Bryce Cogswell. (I actually had the pleasure of meeting Mark some years ago when I ran CodeGuru and on top of being extremely intelligent he's also a very cool person).
I don't know what this will mean to who the Winternal and Sysinternals tools will ship in the future - as part of the Windows SDK?? - but will post here as soon as I know something that I can share.