I believe 3D games are just the precursor to more integrated 3D "metaverses" with all participants creating simulations, stories, and educational evironments in many media, visual, auditory, etc.

I believe the Croquet Project has the best software for creating such metaverses.
http://www.croquetconsortium.org/
http://en.wikipedia.org/wiki/Croquet_project