Hmm. How many editors people actually use these days don't have a usable Lisp mode? I don't think your choices are limited to Emacs anymore. I'm fairly sure Vim has one; I don't know for sure, but would be very surprised if Eclipse didn't; not sure what else people are using.
If it really is the case that all Lisp needs to really take off is editor plugins for IntelliJ IDEA and Visual Studio -- hmm -- maybe we should do that.
That's the real barrier, IMO. Who wants to switch editors just to learn a new language with an (apparently) impoverished syntax?