Too bad GuileEmacs[1] project didn't take off. On the other hand, there is an Emacs rewrite in Rust[2].
[2] is also going nowhere since again no Emacs core developer is interested in it and to top it off, they’re well on the path to creating something even more complicated and harder to understand than Emacs’s C core.
These are _good_ developments since GNU Emacs is progressing rapidly on its own merits.