Could say the same about languages you code (cough; php). It's important to question people. People have a habit of just repeating things they hear. Infact.. C# is listed of one of the most highest in-demand jobs at one of the biggest job tech sites: http://www.jobserve.com/gb/en/Job-Search/
I haven't coded PHP for a long time, but ok.
By the means of "die out soon", then I mean the language itself, and not it's environment, jobs or whatsoever.
PHP is already dead by now, but it's still a highly anticipated coding language.
There's a reason why big game engines like Unreal prefer C++ over C# that Unity formerly use.