Just a copyright law note here about the GMR and the elements that are MGM related.
These elements (Oz, etc) will not necessarily have to be changed if the decision is made to drop the MGM title. The license for the MGM logo and name on the park is separate and distinct from the individual licenses of MGM film properties for specific rides or displays. The park name agreement is trademark related while the rest is governed by copyright agreements. Like the licenses with LucasFilm for the Indiana Jones elements, these licenses for ride elements will likely have their own rules, terms and time tables that differ from the agreement that places the MGM name on the park.
Now, Disney may -- if it changes the name of the park -- want to rebrand the ride using Pixar titles or Disney live action film titles and may make decisions to change ride elements. But many people, even film buffs who love the great movies, don't quite associate WIZARD OF OZ with MGM or Casablanca with Warner. Disney may just keep it the way it is because of how sweeping the references are to American films.
A long way of saying that a name change will not have to equal a ride change.