Why not fit both in the same package, as promissed for the One back in 2013?
Also, yes, there will be "this game only runs on XB4", just with "if you are offline" added ahead.
PS will reign with little competition again, MS is already trying to shoot its own feet with 2 different systems to mess consumers mind.
Actually , in my opinion it's smart move, the streaming device will be a super cheap one. I can see PS will follow the same suit because PS already has the foundation with PS Now and they had one before with PS Vita TV