I personally think Python syntax is kind of unintuitive, especially when it comes to matrix operation, and I never get the point of 0-based indexing. I used to consider teaching Python instead of R to undergraduate finance major students, but the feedback was not good so I gave up. However, I still think Python is a great glue language and most of heavy duty jobs can be done by C or Fortran, and what Python excels is to provide API to packages written in C or Fortran.
Why there are more python users than R users? Because there are more cs guys than statisticians. Why there are more python users than Julia users? Because there are more cs guys than mathematicians and engineers.
My point is that Julia does not have to aim at an user base larger than Python. If Julia can attract most Fortran and Matlab (or Octave) users, then I will consider it a huge success.