From what I've seen Open Beta should be early to mid '09, with release coming after Stardock and GPG are happy with the results. Keep in mind that Stardock does not use their beta's as 'early demos' they are in fact, BETA testing. Typically early builds are just to stress the engine and host computer, and then they start adding in other stuff to make sure it all plays nice.
This'll probably get my money on release, if for no other reason than because Stardock is publishing it. I just plan to wait until release, I really have no interest in beta testing anymore.