I'm not sure that if the cinemas did stop 2d showings whether ticket sales would take a significant hit. I dislike 3d, but will go and see a film in 3d if it's something I want to see and there is no 2d showing available. I suspect the cinemas have an agenda of pushing it as they would have forked out the money for equipment that they don't want to see wasted.
Hopefully if 3d is here to stay, filmmakers will be start using the tech in a more intelligent way and cinema chains will learn to set their equipment up properly. I'm particually sick of shots in 3d films which are contrived to have something poking you in the eye, particually when watching it in 2d as there is nothing which drags you out of the film than thinking "oh look, that would be poking me in the eye if I was watching this in 3d. As it is, it's just a dude waving a sword around for absolutely no reason".