Stephen J Turnbull <turnbull(a)sk.tsukuba.ac.jp&gt; writes: ... To give some idea about how long a "long slow migration" can be, there was full "C" mocklisp (either the predecessor of Emacs Lisp or something else pre Emacs 17) support in XEmacs until last year and token fragmentary Lisp support of mocklisp-isms is *still* around. My guess is that given any kind of compatibility, there will be Emacs Lisp around pretty much forever. If we started reimplementing today, maybe 5 years from now a majority of the code would be natively written in the new extension language, but I doubt it. This is going to be a long-term project. You're probably right on that. It could also theoretically wait on improvments in Freed CL implementations too.