The demand for lisp in emacs is overrated by a vocal minority. Most people using emacs do it for the things which are not lisp-specific. The features, the plugins, the community. All that works without touching elisp as a user. And even the swallow elisp-contact that most user have when writting their init.el could be done with any other language.

Though, it's true that the many elisp-code around usca heavy burden. But how much of that is actually still used? And how fast would a propsering community replace them really? Hacking-friendly tools tend to have a wild growing ecosystem. Emacs itself is not shy of having many clones of similar featursets and regular new implementations of old but still popular features.

In that view I don't thing a new language would a real problem long term for the prosperty of emacs. It might be even a benefit, as it mixes in new blood, more people and a broader ecosystem from outside the emacs-scope.