From its inception Guile was aimed to become the extension language of the GNU System, including eventually that of Emacs. While the latter is not yet a reality, the idea is in the GNU hacker Zeitgeist.
Recently, Emacs developers discussed about a possible integration of Guile in Emacs, which led to interesting discussions: http://lists.gnu.org/archive/html/emacs-devel/2010-04/msg00665.html .