Well, it's hard to overcome the kind of inertia that Python and R have. So I think it can go either way.
(Imho that inertia is the whole reason it's still Python and R, rather than just Python).
But I think that if some language disrupts the status quo in the field, it'll be probably be Julia. I think it has many of the important qualities
except the most important one
Honestly, I don't think the difference is big enough for the switch to be fast, but I think new users who haven't already invested a lot in py/R may prefer it and cause it to grow.
Jason Knight posted a question earlier this year, perhaps he can say smarter things about it than me.