XBOX is interesting in that it does make money, but it is the brand recognition MS is using, XBOX brings to mind a younger generation then what MS usually has access to.
Surface is fine. Tablets will at one point become the single largest mobile personal computer, and bailing on that market would be dumb. The Surface line needs to be premium though.
Bing is the service i do not think people truly understand. It is not just a search engine,although it is a good one. It is Microsofts "data coordinator" that is incorporated through it's massive infrastructure into almost all it's device. Like XBOX gamming online? Looking excitedly to Cortana virtual assistant? Like Local Scout on your maps? Just a couple of examples of Bing at work. It is used in MS cloud-based business intellegence bundles, and also Office 365 intergrations.
Of these three, Bing is by FAR the most valuble, especially after nearly 6 years of investments in it.
So long as MS intends to make continued gains in the consumer field (and all indications is that the new CEO will have free reign to decide how that is to happen, but would not have been hired unless he/she agreed to make it happen, and Mr. Nadella made a point to emphasis during his first presentation that he viewed consumer market as vital), then you can not shed XBOX.
You could live without Surface. Other OEM would provide Windows 8 tablets just fine. But if you are going all in by buying Nokia for smartphones anyways, why not make a tablet line and enjoy the profits?