I doubt that the pro machines and the cinema displays will go to a glossy-only configuration. Like others have said, Apple would want to give the option to those users whether or not they want something that displays colors in a more traditional sense like a matte screen or one that alters the colors like a glossy screen.
Personally, I hate the glossy screens and it is my sole reason why my next computer will not be a MacBook but rather a MacBook Pro.
I dont think they will ever become glossy because some people that use the "Pro" models would much rather have a matte display rather than glossy because matte displays "true" color. If they did go all glossy (which I don't think will ever happen), I will just buy a refurb.
I do have a question, is there is cost difference for Apple to make consumer products glossy to save money? Just wondering.