Recently, there's discussion on Emacs dev forum about switching to Guile, a Scheme lisp. Of course, such discussion always sparks controversy. Namely, the Common Lisp camp isn't happy. Among the posts in the emacs dev list, those by Thomas Lord has some good info of emacs and Guile history around late 1990s. See: emacs dev. 2010-04-11, Thomas Lord.
Here's the post that the Guile's current maintainer, offers his help on this and why he thinks it's a good choice. emacs dev. 2010-04-14, Andy Wingo.
Whisper to myself: please don't f��� up, please don't f��� up.
I hope the emacs maintainers would just let Andy do his work. In non commercially backed open source projects (⁖ not Google, Firefox), there's always huge number of opinions, ideologies, arguing and arguing for years, nothing gets done. What actually happens in the end is whoever wrote code and made things work, ends up as real progress; bad design choices or other problems not withstanding. Ideology and “good” design oriented intentions usually don't go anywhere.
From my own experiences, i find it true of Thomas's account of the late 1990s history of gnu language. I also think moving to Guile is the best practical choice for emacs, in particular because there's someone willing and able to do the work.
It's been 10 years. Sun Microsystems, once was trying to kill Microsoft, is now dead. (am very, very glad. There's no commercial software company i hate more than Sun Microsystems) Perl, once was the craze and number 1 scripting language, is now barely heard (am also very, very glad). For detail, see: Language, Purity, Cult, and Deception.