In Lord of the Rings: The Return of the King on the way to returning to the Shire Gandalf tells the hobbits that:
But if you would know, I am turning aside soon. I am going to have a long talk with Bombadil: such a talk as I have not in all my time. He is a moss gatherer, and I have been a stone doomed to rolling. But my rolling days are ending, and now we shall have much to say to one another.
So does this mean Bombadil is also a maiar like Gandalf? Has his reason been fulfilled and so he is now in rest?