Read "Who Says Elephants Can't Dance", Lou Gerstner's firsthand account of IBM's historic turnaround. IBM was 3 months away from running out of cash when he got there in 1993. It survived largely because he bet the company on a pivot out of tech entirely (the IBM of today is a professional services company) and into a new market where they're not subject to the same Innovator's Dilemma forces.

The same thing could happen at Microsoft, but it's unlikely with Ballmer (or any insider) still at the helm.