Personally I feel characters this old should be moved to the public domain, but maybe that's just me.
This is America. Major Corporations and the politicians they own will decide when and if anything goes into the Public Domain. As it stands now nothing new enters the Public Domain anymore (since the 1994 Walt Disney/Sonny Bono Act) and the Major Corporations are hard at work on recovering anything of value that had already been established as Public Domain. No rest for the wicked.
Judge Otis D. Wright, Judges Stephen Reinhardt, and John Sedwick reverse decisions and find in favor of the Mega-corporation over the creators families. Not a surprise and nothing resembling justice. Money and Power trump truth and justice every time in the U.S. court system and will continue to do so. The Heirs were robbed by DC Comics and then the Court System.