Gandalf's First Sacrifice

[Inziladun]

I am currently re-reading The Hobbit for the first time in I couldn't say how long. I've just gotten to this part, where the goblins and wolves have Thorin and Co. stuck in the trees:

Then Gandalf climbed to the top of his tree. The sudden splendour flashed from his wand like lightning, as he got ready to spring down from on high right among the spears of the goblins. That would have been the end of him, though he would probably have killed many of them as he came hurtling down like a thunderbolt.

The Hobbit Out of the Frying-Pan Into the Fire

But for the arrival of the eagles, the implication clearly is that Gandalf fully intended to jump from the tree and try to kill as many enemies as possible, giving the rest of the Company a decent chance to escape.
He faced a somewhat similar situation years later with the Fellowship on the Bridge of Khazad-dûm; similar in that on both occasions Gandalf believed his back was against the wall, and only a sacrifice by himself would allow his friends to have a chance of escaping.
If he had, in fact, been obliged to jump from the tree it certainly would have destroyed his body. Would he then have returned? After all, his task, the defeat of Sauron, was still before him. And if he returned, would it have been as the White? I'm inclined to think no on the last question. Any thoughts?