If they actually release this next-gen I will buy it. We know they have plans to make the Xbox streaming service playable on phones via wi-fi or 4G, I could see myself using these to play Xbox games while lying in bed over my houses wi-fi.
It's certainly an interesting idea for Microsoft to get into the handheld market. Instead of selling handheld hardware, just release Xbox Live/Game Pass to the billions of existing phone/tablet owners.
I wonder if Sony will do something similar, offer Playstation Plus/Now and a detachable Dualshock for phones/tablets, it would be their evolved version of the Playstation Portable line.