The ED!
The plan for this game is to effectively not stop developing it. Besides the first bonus Pack and the simple customisations, I am fairly certain they plan on 4 additional bib bonus packs. After that they may very well start doing some core updates the game engine requiring a follow on version.
Personally the fact that the game allows such simple addition of new features is a major plus. The fact that they are coming out simply means that they were not ready and tested pre feature freeze for the release date. Most companies would have effectively dropped developmental support at that point (Like Quicksilver with MOO3, Lets Lose 80+% of staff before we even release the game.), Stardock on the other hand, plans for continued additions and addon's.
It was always planned (since talk started about GC 3 years ago on the old SD site) that there would be easy add ons and continued developmental support for 12 months + at least through Drengin.:D If they refused to release the (perfectly working and challenging) game unitl they had completely ran out of development ideas (like a integrated MP3 player) then I doubt we would ever see it.
Now MOO3 on the other hand appears to have actually not been released in what I would call a finished manner. Certainly not as far as AI, Gameplay, UI or documentation is concerned

. There is also exccedingly little chance of anything even resembling a bonus pack coming out for it and it appears most patching will be done by the user community through Mods.
Yours
Paul