I believe that Clojure is not the only Lisp build in with concurrency. From what I understand, LispWorks and perhaps Allegro Lisp is also concurrent in design. As for whether the Eclipse Lisp plug-in is concurrent, I am not sure as it relies on SBCL or CLISP for the environment. And Racket is also another Lisp dialect which Prof Matthias Felleisen has assured me that it is also a AI language, but as for concurrency I am not too sure. I believe the way forward other than create a new fork with Clojure would be better to engage the Lisp steering committee to change/add concurrency into the Common Lisp language.