Did Gandalf have a Plan "B"?

[Inziladun]

Welcome to the Downs, d4rk3lf.

This must be the quote you're referring to:

'But all worthy things that are in peril as the world now stands, those are my care. And for my part, I shall not wholly fail of my task, though Gondor should perish, if anything passes through this night that can still grow fair or bear fruit and flower again in days to come.'

ROTK Minas Tirith

I see that as less of a plan on Gandalf's part, and more a profession of hope and faith that his work would not be in vain. I see a parallel with a similar thought from Sam, as he and Frodo approached Gorgoroth in the arid ugliness of Mordor:

There, peeping among the cloud-wrack above a dark tor high up in the mountains, Sam saw a white star twinkle for a while. The beauty of it smote his heart, as he looked up out of the forsaken land, and hope returned to him. For like a shaft, clear and cold, the thought pierced him that in the end the Shadow was only a small and passing thing: there was light and high beauty for ever beyond its reach.

ROTK The Land of Shadow

I think both Gandalf and Sam just realized that Sauron, even with a total victory over the West, would still never be able to control and destroy everything.