.NET may be better one day, but even if a language does go obsolete (which, by the way, hardly ever happens), it's great to learn it. There's always code that needs maintaining. They pay through the nose for good System 370 programmers - US$100,000 / year easily.
Axon described C# as the child of C++ and Java - I do agree that there's a sort of progression there, and as much potential as .NET has - it's not as established as Java yet. I think right now it's already better (although projects like Mono and Rotor aren't quite up to par) - it just not as well known as Java was / is.
You decide, but once again, you need to do more with C++ first.