In 2013 the Siegel and Shuster heirs share ownership of the greater part of Superman - that's the status quo,
Just because you have a pile of parts doesn't mean you have a car.
I've been doing some research and found that the SS heirs actually have less than what appears
What the SS heirs own
The name Superman and Superboy
All the characters in Smallville (Ma and Pa Kent, Lana Lane)
All the Major characters in Metropolis
Lex Luthor
The Suit
The origin
What they don't own.
Superman's flying powers!!! (not part of the original IP) This is probably a deal breaker right there. Other powers like heat vision, X-Ray vision, and freeze breadth.
The Fortress of Solitude
The Rest of Superman's Rogue's Gallery (Braniac, Zod, Bizzaro, Apokalypse, Metallo etc. ) No bowing before Zod for their Superman.
No connection to the rest of the DC universe. That means no JLA, no ass kicking by Batman.
No connection to the past movies so a direct sequel is out.
Hell, the studio's rushing a Superman production right now for very little real reason other than legalities.
The WB is going to lose the rights in 2013 if they don't make a movie.