You already loose side quests you have not completed yet at certain events in the game (like all the dragonslayer side quests becoming obsolete once you become a dragon). Finishing the game would be an event that makes a lot of side quests obsolete I think. So I doubt there is anything left to do.
They could be generating all kinds of quests after that point, but that would require additional QA time as well. I hope they will spend that time on the mod kit instead.
