Why can't Julia fill that role?
Point being that even if Julia is not there to replace Python, there is still a strong case for using it as a way to augment Python workflow.
What you can do in Julia that you can't do in Python is write high-performance library code in the high level language. If you need to write custom code that isn't just using stock numpy or scipy algorithms right out of the box, and needs to use custom data structures and user-defined types, Julia is a fantastic choice. You can try with Cython or Numba or PyPy, but you're either working with a limited subset of the language, or forgoing compatibility with most of the libraries that people use Python for.
Julia feels like writing Python but does not allow some of the semantically impossible-to-optimize behaviors that you can find in Python, and has a type system that you can use to your advantage in designing optimized data structures for the problem at hand.
As to my own experience dealing with data, the degree of freedom, as basically a programmer, is small. Specifically, I have to think and bear tools in my mind from the start. Which might not be ideal, but cant avoid anyway.
I use it because it has quite good numerical primitives, and I can quickly make a slow, Python-like first pass at an algorithm, then profile and get C-like performance in the bottlenecks with minimal effort. And if I need a particular library, I can call Python's. Also: macros and multiple dispatch make a big expressiveness difference for my type of work.
C++17 also feels surprisingly dynamic, and together with Cython for easy Python-C++ interop also decreases the need for Julia.
And reports from the Julia world are not exactly encouraging - http://danluu.com/julialang/