That is true, but the author made it look like Microsoft was either currently, or close to, suddenly falling off of a cliff. And the market they are in will likely remain quite large for at least a decade. Despite all of the predictions of tablets somehow severely cannibalizing the PC market, I simply don't see this happening. Corporations will almost certainly not move in any large numbers for a while since they move at the pace of molasses to new technologies, and corporate sales are one of Microsoft's biggest areas. As far as consumers go, I haven't the faintest idea what they will do so I will not speculate on that.
As far as Jobs goes, his health appears to be deteriorating rather quickly. And assuming he has as much of an influence as I think he does, that could be a problem.