RonCaird
I'm afraid that this is too much of a niche market for a company like Microsoft. They make software products that sell millions of licenses, not thousands.
I actually think it makes sense for Microsoft to buy Sonar, for the same reason it made sense for Apple to buy Logic.
Microsoft have an image problem they're desperately trying to shake: they don't want to be the staid manufacturer of computers your boss makes you use, they want to be the preferred option for creatives. Apple have been rapidly losing the thing that makes Apple cool- the creative industries. Apple are cool because of the people who used them. However, Apple have long been neglecting that market, whereas Microsoft have been embracing them.
Look at Microsoft's investment in hardware (e.g. Surface, Surface Studio), industrial design and pen integration and they all point to the same thing. And whilst Windows has a number of Windows-only offerings in areas like CAD, they really need a Windows-exclusive video editing package and DAW, and Sonar fills that gap.
Think of it more like a marketing investment for MS than a profit maker ;)