Huh? Nobody is writing numerically intensive libraries in Python. Clearly this language proposal is taking aim at C++ and Fortran. Even if this caused TensorFlow & others to rewrite everything in Swift, people would write Python bindings to it and keep using Python.

I'll get excited if Apple actually merges this into Swift. It's a niche feature that their compiler team will need to maintain forever. I actually have been working on algorithmic differentiation in C++, so it's not even that I wouldn't want to try Swift out if it actually made it in. However, because this sort of thing is of such narrow interest I believe the future will stay with embedded DSLs / libraries / ugly macro/template hackery.