Ford CEO Alan Mulally has denied that he's planning on moving to Microsoft as CEO according to USA Today. He said:
I love serving Ford and have nothing new to add to [my] plans to continue serving Ford
Mulally has also previously mentioned that he will stay at Ford until at least 2014, but Microsoft still appears to be considering him. Bloomberg reports that the Microsoft board is looking at him as a potential replacement for Ballmer, but a decision is far from being made.
Alan Mulally turned Ford around, so if the speculation is true Microsoft could be hoping he can do the same for them.