The heirs have already won. Ownership of the first two weeks of Superman daily newspaper comics already reverted to the families.
The expanded destruction of Krypton was defined there for the first time, as well as the names Jor-El and Kal-El. Don't be surprised if the new movie alters his origin for this reason.
DC's right to exercise copyright on Issue 1 of Superman expires in 2013. This issue established Planet Krypton, Clark Kent, Superman, an earlier set of superpowers, Perry White, The Daily Star and Lois Lane. An elderly couple who found baby Clark and gave him to an orphanage on page one are never referred to by name, so Johnathan and Martha Kent stay with DC.
Beginning with issue 2 Superman was created as "work for hire" and all further inventions became the property of National Comics (later DC). This means If the families were to begin publishing their own variant of Superman they would be unable to use any villain or story element created outside those two sources I mentioned. They would not be able to use any costume or S shield designed by National/DC/WB after issue 1. Superman's supporting cast outside Perry and Lois would be off limits (Jimmy Olsen).
DC's strategy for 2013 might be the reason they just rebooted the universe.
Neil Gaiman won a lawsuit recently against Todd McFarlane that might explain the recent DC reboot. Gaiman created Medieval Spawn and McFatbrain created a bunch of merchandising and tried to cut Gaiman out of the loop. Todd's argument was is was a variation of a character he created so Gaiman didn't create a new character. A court disagreed and Midevil Spawn was determined to belong to Gaiman.
DC may be attempting to create unique variations of it's entire catalog for this reason. By changing Superman (and everyone else too) they might be able to convince a court they are no longer using the same versions of the characters created in Superman 1.
Not only have the Seagal and Shusters families filed copyright claims, so have the Kirby kids. The Kirbys have also filed against Marvel Comics their intention for copyright revocation.
If you think DC is screwed, imagine Marvel without the characters Jack created. Yikes. Spiderman and Wolverine are going to be busy.
Who the hell made those other 3 Supes there? 
