PEP 750 started its life in part as a result of learnings from pyxl [0], which used some clever hacks to add a JSX-like syntax to Python.
In the end, my instinct is that t-strings are the better more generic feature to add to the language itself today.
That said, I'd love to see the Python ecosystem get to the point where it's relatively easy to implement transpilers and get new grammars integrated with key tools (colorizers, formatters, linters, type checkers, etc). After that: let a thousand JSX-likes bloom.