One of the the biggest features of WP7 since the beginning has been the Xbox Live integration and its games. Although, I haven't heard of too many great games for WP7, at least in the beginning it showed some potential. Plus, it offered the advantage of playing whatever games they had for it, with your friends, and keep track of scores and achievements.
So in what I consider a smart move, Microsoft has decided to bring Xbox Live games to Android and iOS, too. If it's not already dead, this will probably end WP7 for good, by taking its only major advantage. But let's be honest here. WP7 has gained no traction whatsoever in over a year. It still has the same market share as at launch, which is less than Bada, and much smaller than WebOS in its first year. So that says something.
Now, the Xbox division on the other hand, is a pretty big part of Microsoft. They also don't make a whole lot of profit, so they need to keep expanding that Xbox business to make it more profitable. And since WP7 is not doing that well anyway, I believe it's very smart to bring the Xbox Live games to Android and iOS, too.
Microsoft is also considering bringing Office to the iPad, and once Android tablets start selling in many millions, I doubt there would be long before they bring it to Android, too. Whether Windows 8 fails or succeeds in the market, it would still be a huge missed opportunity for Microsoft to allow their competition to Office to dominate Android and iOS. Whether Microsoft likes it or not, both Android and iOS will be on billion+ devices in a couple of years already, and that's a huge market they could miss.