I doubt that. It's certainly the trend and a lot of new code is produced in Python. But most models will run on R/Matlab/C++/C#. I'd guess that most quant departments have less than 10% of their code in Python.
But Python is the modern way to go, so every shop stresses that they use it and they expect every new hire to master it.
In addition, although that's often not possible. You need people who can write C++ to maintain code. But it's hard to find because few people with a finance background have any experience with C++. So companies often end up developing in python and then passing it to developers who port the code to c++ for speed and to fit it in the existing framework. If they could be replaced with Julia, it would potentially save a lot of money.
But Python is the modern way to go, so every shop stresses that they use it and they expect every new hire to master it.