Tommy Vercetti
The Don
Microsoft won't fail ... just that they need to adjust to a post-PC environment. IBM had to pretty much do that when post-main-frame era came as well, and look how well they are coping now.
Microsoft have a lot of strengths still in the corporate sector, where Windows/Office/Server, etc will still be required.
As to Tablets/Phone, that battle is already lost to Apple and Android, who are continuing to grow. As to the XBOX, it is just a toy and a very small part of microsoft revenue stream.
I don't think the PC is going anywhere. Tablets are for consumption not production. Metro UI should be scrapped. It is horrible.