Now as to the question of what stack to invest in from a career standpoint... my guess is that Python would still give you a very good ROI. Look how popular it is in the machine learning / data science world, for example. I'd bet there will be more jobs for Python coders than for Julia coders for at least another 5 or 10 years or more.
But hey, hedge your bets... invest in something for today like Python, but start spending a few cycles here and there on Julia and Go. Flexibility helps in this field. In my 17 some odd years doing this stuff, I've gone from focusing on C++ to mostly Java, then to Python, back to Java, then on to Groovy, and now am using Java, Groovy and Python. But I'm also spending some time on R, as well as Julia, Go, and Rust, just to stay current.