What I see is a marginally profitable business (finally, following years of huge / $4B per year losses) that obscures google's true monopoly in the US. For all the claims of 20% search marketshare, on my personal blog, google has 98.7% marketshare in the last 10k search visits. It's an open question if bing is worth the hassle -- is it foreseeably profitable enough that msft should continue in that business?
imo, it would quite damaging to google if msft shut bing down, reallocated the engineers to more profitable projects, and let google own their 75% + bing's 20% == undeniable monopoly search marketshare, with the immediate antitrust implications, in the US.
Microsoft's biggest threats appears to be things like chromebook, google apps, and ios/android rendering windows and office largely unnecessary. I don't see how having a search engine helps any of the above.