Y'know what? I probably would suggest to struggle with C++. Purely because once the struggle is over, your software will always work. You can happily reuse your code for the next project too. Just switching language to help you achieve a short term goal is IMO not a good solution. Not to mention, C++ doesnt have anything in the spec to cause a developer to struggle more than any other language ;)
if you can get stuff done quicker and more-effectively in C#, Java, or Python and you can get the performance you need, then its more effective to do that than struggle against C++'s idiosyncrasies and c'est la vi attitude just because some dude on a forum told you its more hardcore.
C#, Java and Python (reference implementation) are all written in C/C++. There has got to be a reason for that. Not to mention it is very hard for Python to use Java or C# libraries, whereas they can all use C/C++ libraries very easily.
Poorly-informed, wannabe *nix wags are not any better than "trendy hipster developers".
In the OP's original list of operating systems he wants to support, all of them are UNIX-like apart from Windows, so *nix is becoming more and more relevant (us wags must be doing something right! ).
Unless our goal in life is to learn every language under the sun, I suggest we spend the time to become even better at C++ instead. Not to mention the fact that C became instantly more popular than Fortran from day one.
If you're argument boils down to "C++ will never die", perhaps you should take up Fortran as a hobby -- that's been around longer than C++, and still has a strong showing in certain circles (Finance, Scientific computing).
This argument has been done many times before and especially since you have used and know the benefits of C++, it will probably be taking this thread a bit off topic.
I think the real question is if certain platforms will even let us choose the language. iOS and Windows 8 (especially mobile) is making it very hard to use a single language for every platform.