They couldnt get a standardized scenegraph API off the ground last time ... without that you can forget about getting standardized interfaces to physics/3D/-sound engines.
2) What form will this controller take? Something MS will produce itself, or just supply a reference design to other manufacturers like Logitech/Saitek? Or both?
Developers and Publshers for all platforms have asked for this - that's the main genesis behind XNA - it's another thing that makes sense for helping developers standarize the way they develop games.