Well, I think this actually makes some sense at the moment. MS is doing well now but heavily centric to US and handhelds is a really tough market to enter. The odds would surely be against MS making much headway with a dedicated device, at least initially.
With Kinect doing well I just figure MS:
- don't want to mix a successful second gen home console battle with a very tough, entry level fight
- want to use the Live link to promote Windows 7 Mobile more than they want a handheld
- have more interest in protecting their interests and standards in the growing smartphone area than the traditionally more isolated and self centric handheld area
So pushing Xbox brand via Windows 7 Mobiles makes sense. Looking at release of 3DS and PSP2 MS would need to add serious tech investment to their plate too.
All in all, even allowing for MS resources, the handheld space just feels like a stretch for them at the moment IMHO.