Superheroes in the Public Domain?

It's not just the DC characters WBD has to worry about, it's also Bugs Bunny, Daffy Duck, Porky Pig and Tom and Jerry in the near future.  Unless copyright law is changed again Mickey Mouse is going to be the first real test to things but (I'm going to go out on a limb here) I don't think much is really going to change.  So Steamboat Willie will go out of copyright in a couple of years, it doesn't mean that Disney is going to lose the trademark on the Mickey Mouse name or the copyright to anything that was created after.  Yeah, sure material will continually fall out of copyright but the trademark on the name and use of the character as a corporate mascot/logo won't go anywhere as long as Disney keeps them in use.  I don't see any of the major studios making any kind of Mickey Mouse content just because they can't fully own it or merchandise it.  I'm sure that there will be smaller companies that will try but the power (and near bottomless cash) of Disney's legal team will keep most at bay even if they are in the legal right.  Another thing to look at is the Fleisher Superman cartoons.  Those have been public domain for decades and they're available on DVD with images that are clearly Superman on the case along with the name with no money going to DC.  Tarzan also comes to mind, the story is public domain but the Burroughs family holds the trademark on the name so no one can fully make use of the property without making a deal with them.  Seems to be the same way with the Baum family and the Oz stories and characters.

I think what may be a bigger deal, especially with Superman, is how falling into public domain will affect creators' rights.  Will the Seigel and Shuster families lose their claim to the character completely to WBD's trademark filings?