I really have no idea but when and how do they create new languages! How long has C++ been around for? How about Java?
A good question, I will consult google for you
There are MANY languages, and there are always new created languages, but they are usually not good enough to replace C++, Java etc.
I think since 80...
Er, '85 according to Wikipedia...
It depend on what kind of language you want to create? if it's a full blown new language from scratch or if it's a set of libraries based on another language for example.
I think that they make them by coding in binary, very difficult.
I don't think that there is much demand to replace the current languages.