I wonder whether this will end up being a viable language for people who just want to write fast general purpose code with Python's syntax, and not write any AI/ML-related stuff.
Hard to say, as far as I can tell there's no networking libraries right now.
AFAIK, it's a general purpose language. I don't see any reason you wouldn't be able to use it for applications outside of ML.
Well there are countless obscure general-purpose languages and language implementations. What I meant by viable is that the user won't feel like a masochist because of weak tooling and library availability.
The goal is to have Mojo be fully compatible with Python, so that you should eventually have access to all of the libraries offered in Python. How many libraries will be written in Mojo remains to be seen, depending on whether it catches on or not.