Anyone who has worked enterprise in the eastern half of the U.S. knows better than to be worried by this. There are so many mission-critical business applications written in C#, and even VB.net, that the idea of .NET jobs going away in the next 15 years, even if MS were to abandon the product today, is nil.
Where I live I would guess that at least 90% of job postings for programmers are .NET.
Where I live I would guess that at least 90% of job postings for programmers are .NET.