Good choice, leaves space to rewrite in rust later, right?

The fact that this is so common I think yearns for a language that is basically python and rust smashed together where a project would have some code in the python side and some code in the rust side intermixed fluidly like how you can drop to asm in C. Don't even really try to make the two halves of the language similar.

An embedded interpreter and JIT in rust basically but jostled around a bit to make it more cohesive and the data interop more fluid— PyO3 but backwards.

You can already do that with a macro: https://crates.io/crates/inline-python

But I'm doubtful that it's going to make things simpler if one can't even decide on a language.

It's not really a "decision" thing, more that the pattern of write most of the code in python, rewrite the performance critical bits in rust as a cpython extension would be nice if it were made first class.

Maybe something will eventually crystalize out of mojo?

No need.

Future of development is going to be Python -> optimized machine code. Its already possible to do this with LLMs with manual prompting.