What I meant is that as long as there is a need for such a pronoun to exist, there should have been some kind of borrowing or inventing. You know, when a language lack a term, it is usually borrowed or sometimes invented.
I see what you mean, but the problem
(as you called it earlier in your post) of not having such a pronoun might not be regarded as a problem by all. People have got used to using the alternatives you just provided (they, he or she, etc). Even if this is a real problem, it is not easy to make predictions what will happen to the language to solve it. You might still ask a linguistic expert about this, as s/he
must be prepared to give fuller answers, but I think the gist of that answer would be just sth like I mentioned. Even linguistic experts find it quite difficult to make predictions about languages; they are really much better at explaining the phenomena that have already occured rather than the phenomena that will happen!