Does anyone have any reasoning for their guesses?
The only way we know to currently stop the zetsu is to poison them. Only madara and Kabuto know about this. Maybe someone in the hidden leaf will know something about the wood element and how to stop it? I'm not sure if the alliance even knows what zetsu is made of.
So far the zetsu seem like a nuisance while they are trying to deal with the real threat of kabuto's zombies.
The zetsu's arent immortal right? There's just a butt load of them. So they'll deal with them all eventually.