Java succeeded on mobile (Android) and on the server-side. C# is very successful on Windows both on client and server side.
>I'm talking about "next C" which means that either it replaces C as program-development language or it replaces it as OS kernel-level language. AFAIKS Java and C# both failed there. Spectacularly.
You don't need to replace C as a language for the kernel (though C# can be used even there - see Singularity OS).