X11 applications don't open after XQuartz update (OS X 10.10.4)
I'm afraid you'll probably need to rebuild emacs.  I expect that the one you have is looking for libraries that aren't there any more following the XQuartz update.

I had the exact same problem, and solved it with brew upgrade emacs --with-x11 --with-ctags --with-glib --with-gnutls.  The relevant command-line for you will differ according to your choice of package manager and build options.