Python is dying in much the same way that C is dying, and by that I mean it's not dying at all. I'm no expert on Go or JS but Julia is not even close to being a serious competitor to Python for data science right now. Besides, Julia has a role more similar to R than Python.
I think C and even C++ are basically dead from a job market perspective but seem alive and doing ok in the opensource community. The need for paid C development pales in comparison to the job market for python. The industry, at least outside HN, for "backend" type work has settled on java/.net languages. They are just good enough for 95% of use cases and easy enough to hire for.
AFAIK, for a competitive backend programmers, besides C++/Java, good at least one script language(tool) is a must, let it be bash/perl/Python, etc... More and more people are picking up Python for this role, simply because it is more a complete package than its competitors.
I do agree with you, knowing ONLY Python is not really something to feel good at, but same thing can be said for any other programming language...
