As an emacs addict/user, what I really want is a credible alternative to that cockroach of editors. Price of admission: run in a terminal, run graphically, run on every possible system, be open source, be ridiculously, easily extensible. What a successor might add: Not be riddled with bugs. Not be ridiculously, terribly bad at actually displaying text (quickly, smoothly, large amounts). Not be extended in a language…
If you don't mind the lack of extensions, and are willing to write your own, you may wish to try some of the other emacsen associated with the lisps. Hemlock is CL-based, so likely faster than Emacs, and Edwin and Guile-Emacs are both based on Schemes (edwin is MIT Scheme, Guile Emacs is... Guile). They still suck at some stuff, though, and they don't have the massive plugin ecosystem.