As someone foolish enough to build a production-grade tool with arc back in the day, I'd say that Clojure has taken most of the best ideas from arc already.

I think arc still had few good tricks related to code brevity though that never got adopted by Clojurists (they would require a custom sexp reader to be bolted into Clojure to port them) but almost all of the other good stuff from arc made it into Clojure, and Clojure had many fantastic ideas that greatly improved on arc.