Arrandale 32nm Westmere generation CPU with 45nm graphics and Calpella platform will have support for switchable graphics. Arrandale will also have its own integrated IGP, that sits on a CPU but if this is not enough you will be able to use discrete graphics.
Currently Intel uses mostly ATI's switchable graphics and this is the way to use discrete GPU when you need performance, and when you are not playing games, the platform can switch to an IGP on Arrandale CPU.
There is a big chance that Intel might be supporting its own Larrabee, but we sincerely doubt that they can have mobile chips in early 2010 as we expect Larrabee to be big and hot. Still, we can be surprised.