Julia isn't that much positioned as an AI language, it's more of a numerical analysis and scientific computing language at this point competing with matlab, which is something that doesn't go through hype cycles. The fact that it's so well positioned for AI research is the result of that focus (high performance, expressive, interactive and math focused) plus being heavily inspired in Common Lisp, which means the language can be easily extended for new purposes (and CLOS was a brilliant system that didn't get the attention it deserved in the mainstream).

Python is the AI language, and it's already more than large enough to survive many AI winters (plus "AI" is more powerful and useful every winter).