I expect Nintendo is going to have a combination of bundling (Wii Fit) and price reductions to promote sales because they're already very close to a mainstream price and they will want to encourage high adoption rates of add-ons. In 2 years the Wii will likely be $150 to $180 and will be bundled with Wii Fit or an additional Wiimote and Nunchuck.
Microsoft is caught between a rock and a hard-place because they're expected to be profitable this generation and they're already deep in the red. To a certain extent, I anticipate that Microsoft will try to maintain their price level by adding additional functionality rather than push large price cuts. The XBox 360 core may be $200 by then but I anticipate that you will still be paying $300 for the 'real' XBox 360.
Sony is becomming impossible to predict because every positive move they make includes a very negative action within it. I would not be surprised to see a $200 PS3 which is stripped of a large portion of its current functionality, and I wouldn't be too surprised to see it sitting as a $400 system with a 1 Terabyte hard-drive ...
