Yes, so to me, the key question is not whether Swift can replace Python's role, but whether it can replace C++'s role, and thereby also making Python's role unnecessary and solving the two-language problem in the process.
So I think that's the good news--because of the more independent nature of the work, you generally can win data scientists over to a new language one at a time, you don't necessarily need to win over an entire organization at once.
Getting a company or a large open-source project to switch from C++ to Swift or Rust or whatever, seems much harder.