Nah, I don't think he'll be offered a last-minute way out. I see it happening something like this:
The Destroyer shows up and wrecks some stuff. The Warriors Three and Sif try to distract it so Thor can get away, knowing the Destroyer would easily kill him in his powerless state. But the Destroyer tears through the other gods in no time and Thor, realizing that Jane and all the humans who've shown him such kindness would be killed if he runs, turns around and faces the Destroyer. That crucial decision--to try to stop the Destroyer, even though he knows it will likely mean his own death, in order to protect the others--is what finally restores his worth. He's lost his arrogance by showing he's capable of putting others before himself, even to the extent of sacrificing his own life so that others can live.
The best would be if Mjolnir actually returns to his hand on its own right at that moment. The Destroyer advances on Thor, its visor open and its disintegrator charging... and then it suddenly gets knocked over and faceplants as Mjolnir zooms through it back to Thor's hand. Cue giant lightning strike and flannel-wearing mortal Thor is replaced with the fully armored godly Thor again, who proceeds to kick the everloving s*** out of the Destroyer.