Radagast's ultimate fate

[doug*platypus]

In the spirit of speculation rather than textual citation, I would hazard a guess that Radagast remained in Middle Earth out of choice after the fall of Sauron, so enamoured was he of the beasts and birds in Mirkwood and around. Whether he actually did help out in the rehabilitation of Mirkwood after it's rebranding as Greenwood the Great is a matter for even more speculation, but I think it's highly possible that without Gandalf and Saruman around to guide his actions, he just did his own thing. He seems to play the part of the disengaged employee in modern terms. As mormegil put it so well in the other thread:

The comparision [sic] between Radagast and Sauruman is equivalent to the difference between a sin of omission and a sin of commission.

Radagast was a failure not because of his actions as Saruman was, but because of his inactions. Not that he was no help at all, it's just that as far as using his abilities to their fullest, he was no Gandalf to put it mildly.

I imagine that eventually over the years, Radagast, Maia though he was, faded as did those of the Firstborn who remained in Middle Earth through the ushering in of the Dominion of Men... what was it, dwindling to a rustic folk of wood and dell. It is possible that eventually when his body faded, which I believe it would do as he was sent to Middle Earth in the form of an old man with the other Istari, with the sole purpose of fighting the good fight against Sauron, that he was able to seek admission back to the Undying Lands. Would his enquiring spirit be swept away as Saruman's was, though? I cannot say. But I think he would stand a better chance of forgiveness and acceptance.