It would be nice if they handed the spore community the game's internal devkit. So that we could go through it's source code and fix whatever problems the game has ourselves, maybe also make better mods with it too.
A sequel isn't impossible. EA/Maxis doesn't have to start from scratch, they could use what they have now and build upon it and fill in the gaps. This could be done by another studio if it has to (I'm sure EA could gather up a handful of the old dev team to help the new team with whatever old tools or assets that needs elaborating)