Is it still truly mainstream, or have C++ users, at least on Microsoft, mostly migrated to managed C# code?
Certainly at the company I work at, there's been an active migration over maybe the last 5 - 6 years to C# from C++, though we still have millions of lines of C++ / MFC / WinForms code in the primary application I support and help maintain.
Career-wise, I'm quite happy to stay with C++, as it's been my experience that I can throw together utilities that run with minimal, run fast and are reliable, just using C++ and the standard libraries.
As far as writing Scala or Python, Why write code that goes slower than it needs to?