Oh, I agree, DC is running away from Superboy at light speed.
Yes, but I don't think this is because the Siegels got ownership of Superboy. Even after the ruling, they still published Infinite Crisis (and graphic novel collections of it) containing two Superboys. There is also the possibility that Smallville could be ruled a Superboy show and that the Siegels would own all post-2004 episodes.
DC has been erasing Superboy since the mid-1980s. The last retelling of Superman's origin to include Superboy was 22 years ago in Superman: The Secret Years. Despite a 40-year run, no Superboy archives have been published...the only major Golden Age character not to have that luxury.
The market for Superboy is still there. I wish that DC would realize that.