Too much useful work is already done in elisp. If emacs maintainers were going to move to CL, they'd have to make sure that nothing breaks, otherwise it would almost surely result in fork.

> Too much useful work is already done in elisp.

I'm not contesting that, just saying that it is a pity (from the perspective of the wealth of the overall Lisp ecosystem) that all this valuable work has been done in Elisp and not in Common Lisp. Moving to Guile will probably take several years, and even if it really works some day, it will be just another insular Emacs-only solution, because nobody else is using Guile. It wont benefit the overall Lisp ecosystem in any way.

Specially when there's an effort to use guile (scheme) in emacs: http://www.emacswiki.org/emacs/GuileEmacs

I wonder if there'd be a way to create an interop mode, which might look something similar to the way they are handling the lexical vs dynamic scoping.

That way authors could transition from elisp to common lisp.

There's already an effort to do this using Scheme, it's just not ready for this release.

Is CL really that much better than Scheme?

Not from a language-theoretic standpoint.

From a pragmatic standpoint, all standard-conforming Common Lisp code runs on a conformant implementation. Schemes often tend to diverge (and they have 6 different Rn standards). So I think CL is 'better' than Scheme, for that value of better.

I get the appeal of moving towards a more general lisp dialect, but does it have to be CL, because Scheme seems pretty reasonable too, which there are also full-fledged GPL implementations owned by the FSF. And there's already an effort to move Emacs to it, it's just not ready yet.