Hydro, that would be a horrible idea.
There are a few ways that idea could be possible, none of which would work.
They could make it an option in game - Do you want to play the scientific spore or the cute spore - But that'd essentially be two different games sold as one. It would either require double the resources to produce the game or the quality of each respective title would drop drastically.
They could sell them as two separate product, but honestly, that wouldn't fly either.
And at this point, an expansion pack turning Spore into everything we envisioned it to be is also out of the question. Expansion packs add content, not change the very fundamentals of the game.