The basic point of Kinect 2.0 is that in the latter half of the X360s life it had an injection of sales from the casual gamer, 22million+ Kinect units sold, fitness apps everywhere on the 360, a combined 13million sales of retail Kinect dance games. Those are things you can't just ignore when you start to create a new system, the call of duty/gears/Halo audiences were just one group who were enjoying the X360 and buying software/hardware for it, a console where 1/4th of the users in the last years of it's life adopted the Kinect really did give MS the idea that people wanted it and those people couldn't be ignored with a new system.
Then they slapped always online on it at the reveal meaning people who would set the system up for "soccer moms" knew it could cause headwreck having to make sure the system had internet access so they wouldn't be annoyed for tech support then there was the moves by MS to make the system the 1 thing you need in your living room (but you still needed an X360 because of backwards compatibility) but in adding the HDMI input and a lot of non-gaming, non-casual gaming features inside the box they pushed the price of the system to 500dollars at launch, definitely a deterrent from casual gamers buying it for dance games.
tl:dr - I think a successor to the X360 had to have a Kinect, but the price killed the buyers who would have wanted it to have Kinect.
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