As someone who is glancingly familiar with emacs (I have only ever written one elisp function, that too with help) it's a really stupid question, but couldn't emacs have bindings for lua or python or something? That would increase the number of people who can program for it and customize it.

> in 20 years from now Emacs will still be around

I think the real risk for emacs is, over the years, slowly losing the pool of people who care enough to contribute to it -- not just core developers, but also people who write packages, themes, etc. I already see a lot of developers who think Atom / VSCode / Sublime Text is "good enough". You may choose to discount Sublime because it's closed source (I do despite loving it otherwise), but VSCode and Atom are open-source and browser technology is only going to get better.