One thing that we have to remember is that not everything that Microsoft makes capitolizes. Almost 3 times as many people use Apache over IIS. Microsoft didn't develop C or C++. The reason those languages hit it off so big is because they are so readily available. Of course they hit it off big because they're scalable and robust, but many languages have been robust and haven't made it anywhere. You can get C++ compilers for windows, Linux, Unix, free compilers, expensive compilers etc. If Microsoft creates a language, they will likely safeguard it against other companies wanting to create their own versions of it. That will be it's downfall. Take java, you can download JDK for free, you can buy Visual Cafe, JBuilder, you can download Forte. My guess is, if Microsoft follows their current pattern, they will make everything proprietary and that will spell out it's demise. I don't believe who ever spouted off that 95% of people use MS windows. Are you forgetting everyone who uses a Mac or who uses Linux?
Of course, I am from a more Open Source nature so my views are slightly tainted, but that's besides the point. Just because MS makes it, doesn't mean it's best. If MS makes a genuinely superior language and adheres to at least some of the openness that other languages have (such as C/C++, Java, Perl) then it very well may be in contention. But I believe that MS will cut off their own foot and make everything very closed and we'll just have a glorified Visual Basic on our hands.
As far as .Net goes, I'm not impressed. the government didn't let AT&T get away with domination and I have a feeling that they will do the same with MS.
My $.02 (probably a little more even)