Ain't gonna get far once the main developer loses interest in the project. Emacs users use Emacs because they want Lisp and don't care about web rendering and javascript runtimes ... Oh yeah and Rust is thrown in too for good measure.
Good 90% of Emacs code is in the extensions which are in Lisp and nobody is going to rewrite them to Javascript even if the code was running 50x faster.
I'm certain you're telling the truth. And I'm sure that's the case for a lot of old-timers emacs users. But I have the feeling it's less and less true.
People that have used emacs for a long time don't need anything else, so they don't want any change.
People for whom emacs doesn't cover everything want change, but clash against the first group of people (who have been there/contributed for longer), and in the end migrate somewhere else.
But my way of working is : many little projects in various languages, much text reports with Latex/markdown, lots of notes (orgmode), bit of email, bit of IRC. In a traditional business, I'd had to use beefier IDE such as IntelliJ (hat beats emacs without a doubt) and maybe Word. But for the rest, emacs fills all the little holes...
One area where I find emacs lacking is appointment (org mode is too big for little things such as quick reminders for today's stuff); a good calculator (calc is very clumys if you compare it to SpeedCrunch for example); a good calendar (emacs calendar is a nightmare to use, for exampe why on earth doesn't display what happens in a day below the calendar and instead forces me to hit 'd' which opens a new mostly empty buffer...); a good console on Windows (on Linux vterm is mostly perfect). Email support is OK with Wanderlust but a nightmare to set up.
Also, since it's very old, there's this warm comforting feeling that will last forever. And also I'm GPL zealot, which helps too :-)
Given enough time I can make Emacs do pretty much anything. I just don't have that much free time (anymore).
I would love a normal extension language, that also isn’t a hack (like Python integration). I’m not a JS guy but I’ll take it over lisp.
I’m not sure what the web render things are, but if it means some kind of browser integration, that sounds good too. I use org mode, often with html export and latex maths, having it render quickly and seamlessly would be a win for me.
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.
You can have C / Rust / any_lang extensions like RipGrep to boost some intensive workloads as well.
Uh, in the age of the 386 and 4MB of RAM, if you had that setup against a 486 an 8MB, you chose between running X and running Emacs. OFC you could run jmacs perfectly.
It's like saying that a browser skin is "built on Rust" when inside it's still Webkit and Chromium.