How hard would it be for the existing developers of CEmacs to get on board with Rust if they decided to make this the upstream core? I did not study Rust ever but did follow its evolution, and the language seems complicated to me, compared to c.
Emacs is relatively pervasive. It runs everywhere, including plenty of platforms that Rust does not support. Either due to current support priorities or lack of LLVM support.
That makes it something less than a drop-in replacement from the overall CEmacs project perspective. I'm sure Rust devs are working on more platform support, and it's possible Emacs devs are open to simply dropping some of the more obscure targets, but it might be a long time before alignment happens on that requirement alone.
