How do YOU want the Wii 2 to be like

[ChichiriMuyo]

Assuming it's a traditional console and not something else like a VR machine then:

A quad core ~3.5 GHz CPU based on the latest Power PC tech

1 Gig Ram

GPU capable of 1080p output

16 GB or more internal storage

Full backwards compatability with Wii and GC, including controller ports.

WM with Vitality Sensor built in (no finger clamp deal, just hold the controller and it knows)

 

That'd make it noticably more powerful than PS3/360 yet not a whole lot more expensive.  It's very likely that'd cost less than $300 to build today.