I wouldn't place bets on any strategy that relied on Microsoft not closing the doors again at some point in the future, on future versions of their development stack.
Like you said, though, this is better than not having happened.
MS doesn't really make money off C# or .Net directly, they make money off the windows licenses you need to run the resulting code.
Open C#/.Net = stronger, longer lasting community / free improvements = more users = more licenses.
It also has other side effects like fostering [more] open source frameworks/plugins for their platform, which again, strengthens their position.
On this page: http://techcrunch.com/2014/04/02/microsoft-updates-visual-st...
There is this quote:
Microsoft also today announced that Visual Studio 2013 has sold over 3.7 million copies since its release less than five months ago. That makes it the fastest-selling release of Visual Studio to date.
Based on those numbers and the fact that Visual Studio prices range from about $1,000.00 for VS Professional up to $13,000.00 for VS Ultimate, I'd say they make quite a bit of money of C#, .Net (and of course C++ as well).
http://channel9.msdn.com/Forums/Coffeehouse/The-99-VS2012-Pr...
My guess is the actual revenue figures are probably in the $1B to $2B (B = billion) range, which isn't too bad for a product that I'm sure Microsoft doesn't consider one of their big money makers and a product line that I'm sure they also subsidise with income from sales of their other products.
I too suspect Microsoft looks at VS as an essential, break even product, but with sales numbers like that I can't believe they aren't also making a nice little profit from VS.
VS2012 was shockingly bad. VS2010 users who dodged it were now 2 releases behind.
VS2010 does keep me from using C++11 features, but that isn't a massive problem.
Like I said they dont make money off the language or the framework directly it being open source will certainly not hinder or hurt their vs sales. It will most likely increase them.