What language shall I learn to have a job in next 10-15 years?

Depends on the job
Sysadmin you'll definitely need PowerShell and Bash
Webdev you'll need whatever is the new JS framework
C# and Java will be in demand for a while too but I'd rather kill myself than get a C# or Java job
I see Python gaining more and more popularity over time too

None.
Tech is constantly changing, look at the state of IT in 2009 and compare it to today. Unless you want to maintain future legacy systems or be highly specialized expert, like telecommunication dev, you'd be better of being flexible and more versatile: much better job prospects, easy mode in finding new companies to work for. Limiting yourself to one "safe" language or software is a direct way to become an easily replaceable code monkey.

In 15 years? Julia

This user gets it

C, Java, Javascript, Haskell, Prolog

In about 10 years Rust will cover practically every use-case imaginable except programs that require concurrency, in which case you use Go.

This is what people said about Java 20 years ago

This And not being a social autist that can manage people.

Hindi, "क्या आप उस के साथ फ्राईज चाहते हैं?"

The sane man among the insane populace

Learn everything you can about functional programming,

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