Python is the most popular language now, and that gives it a huge leverage relative to anything else. And there are efforts (numba, pypy, etc) that are solving many of the performance problems. So I do think that someone with a couple of years of python experience will more and more be comfortable where they are.
If numba and others were mature as they are now when I first started playing with Python, perhaps I would have dedicated more time to it and would not start learning Julia at all (it took me a while, even coming from Fortran). Now I don’t want to leave because simply I like the Julia syntax better, I like multiple-dispatch, the expressiveness, Revise is fantastic, distributing packages to students or everyone else is a piece of cake, and my programs turn out to be faster than what I was able to do with Fortran (which tells more about how crappy I was writing Fortran, perhaps), because writing, optimizing and testing programs in Julia for performance is much more fun. And I was able to learn a lot about computer programming in general by learning Julia.
In the long term it is likely that most of the problems of every language will be solved, languages will be highly inter-operable, and people will chose one or another for the syntax, paradigms, and expressiveness. Those are somewhat subjective, but Julia is in a good position there, in my opinion.