In comparison to the XBox, the XBox 360's strategy has worked moderately well so I suspect Microsoft will produce a similar system in many ways. I expect they will be aiming for high performance but not at the expense of reliability and initial cost, they will continue to focus on services like XBox Live and video download, and they will try to beat (or match) the other consoles' release dates. Their controller will be similar to the Wiimote+ Nunchuck except with the nunchuck closely matching the functionality of the left half of the XBox 360 controller, and their Wiimote will have four thumb buttons and trigger buttons like the XBox 360 controller.
Nintendo will continue to improve the wiimote and nunchuck in ways I can not (really) predict, and will aim for a high-performance and low cost system; I expect the hardware will be halfway between the PS3/XBox 360 and the PS4/XBox 720.
Sony's strategy will closely match Microsoft's strategy except it will (most likely) release a year later ...
Basically, I expect the following:
XBox 720: Released Q2 2011, High Performance, Wiimote+Nunchuck $400
Wii 2: Released Q4 2011, Mid-Performance, Advanced Wiimote+Nunchuck
PS4: Released Q2 2012, High Performance, Wiimote+Nunchuck $400
