Frodo and the Cracks of Doom

I've been following Andustar's post "lol another one" (what is LOL anyway?) and one particular post caught my eye as possibly deserving more attention. Someone said something like "Frodo was the bearer of the Ring, not the destroyer", meaning that Frodo was not supposed to take it off his finger and pitch it into the lava himself. OK, if not Frodo then who, keeping in mind Gandalf's talk with Frodo early on where he says that to seize the ring from Frodo by force would break his mind.

Maybe Gandalf didn't plan that far ahead, but I doubt it. He must have at least thought about it. Who from the Fellowship would have the unenviable task of wresting the ring from Frodo, if they had got that far?