Did Gandalf have a Plan "B"?

[Inziladun]

Throughout LOTR there is a common theme, at least to me, of people "accepting" the parts chosen for them in the great Play by an offstage Director whom they never see, yet know they still are bound to obey.

Gandalf is the main force in pointing characters to their assigned roles; somehow he has some foreknowledge of who should do what.

He it was who chose Bilbo Baggins to accompany the Dwarves to the Lonely Mountain. When he later learned that the ring found by Bilbo and brought back to the Shire was the One, he felt it to be in the right hands with Bilbo's heir, Frodo.

'I can put it no plainer than by saying that Bilbo was meant to find the Ring, and not by its maker. In which case you also were meant to have it.'

The Shadow of the Past

Having said that though, Gandalf also makes it clear that Frodo does have free will in the matter. He can refuse his part if he wishes.

'And now,' said the wizard, turning back to Frodo, 'the decision lies with you.'

If Frodo had denied responsibility for the Ring, or had feared further involvment with it too much to agree to bear it (both reasonable conclusions from an intellectual standpoint), what other options would Gandalf have had? He wouldn't have dared to take possession of it himself to take it somewhere else.