Um, what? How will they lose their best people? Via layoffs? That's possible, but it's also possible they'll lose a chunk of dead weight in the middle layers.
A lot of the most talented people don't care who they work for, as long as the pay's good and the job's interesting. And Microsoft has a lot of cash.
Initiating a change to a stagnant or destructive corporate culture is a good thing. Whether the results will be beneficial or even more destructive remains to be seen.