Great call out on a reasonable strategy for Microsoft to remain successful, albeit less relevant in the consumer market. (There is another comment alluding to taking the route of IBM, cementing their place in enterprise but sacrificing the consumer market a bit). AD is definitely a great asset that is probably not thought of as much as it should be given its usage, as you point out.

I would say, though, that claiming that IE and Bing advertising is "wasted" is pretty bold. Sure, OSD hasn't started turning a profit yet, but there is something to be said about Bing having ~30% market share and the fact that if Bing did not exist, Google would almost certainly have a complete monopoly on search today. The data generated from Bing and the Bing ecosystem is incredibly valuable, but Bing Ads have yet to unlock the full revenue potential unfortunately. Consider, though, that Google and Microsoft are the only two companies that have the unbelievably valuable asset that is an index of the entire (within reason) web.