Definitely never.
Python is easier to learn. Python is more useful for data munging/cleaning (lower startup time, loads of input libraries). Python has a repl and eval so code-as-data/data-as-code is not an advantage for Clojure as it is over C-alikes. Python FFI is almost free to call into C so end-to-end performance is better than Clojure. Python has the better libraries for ANN (TensorFlow, Theano) and ML (sklearn).
Of course, you can apply "arguably" to every statement in the previous paragraph but the evidence appears to bear it out.
> Python is easier to learn.
I have not seen a learnability comparison between Python and Clojure as first languages. Python is definitely easier to learn as a second language if you're already a trained programmer coming from the C family.
> Python is more useful for data munging/cleaning (lower startup time, loads of input libraries).
Startup time is indisputable, but also barely matters for interactive programming. In Lisps and in Python, I usually just have a repl going for days at a time.
The availability of libraries is not a "never" thing -- it's a "we'll see" thing.
> Python has a repl and eval so code-as-data/data-as-code is not an advantage for Clojure as it is over C-alikes.
You're conflating two different things that people like about Lisps here. Homoiconicity is a separate benefit from having a repl. And though I use it daily, I think Python's repl kind of blows.
> Python FFI is almost free to call into C so end-to-end performance is better than Clojure. Python has the better libraries for ANN (TensorFlow, Theano) and ML (sklearn).
Clojure is free to call into Java. And I'm sure there's a route to C if that small performance boost really makes a difference for what you're doing. Again, availability of libraries is an obstacle, but not a "definitely never" obstacle.
So I don't have a reasonable doubt when I say "Clojure will take not the machine learning niche from Python."
Look at Torch for example. It has been a well established library, and yet because it uses Lua, its future is bleak. PyTorch, on the other hand, is gaining popularity.