Talking to GameInformer, Will Wright said that Spore won't expand in the same way the Sims did, with endless content packs. It's all about going sideways with the soon-to-be-released alien sim.
"I think it will be similar in extent but hopefully not the same strategy we took with The Sims," he said.
"With The Sims, we were basically selling expansion packs to the same customers over and over. I think Spore lends itself more to horizontal expansion, where we take components of the game like levels or editors into totally different formats and hit people that maybe never even played the hardcore PC game, but would enjoy a lighter experience using one of the editors. Or, using the content in new ways outside of Spore the game."
More through the link. Thanks GoNintendo.