It would be remarkable if he returned to the Senate at all. However, if he's in no danger of dying, there's also no chance of replacing him.
That's the political reality.
It would take a Supreme Court decision, and there's no chance that could be rendered prior to the expiration of his term in 2008 anyhow.
My guess is that his political career is over, and he might not even be able to physically sign his candidacy papers for the 2008 election. But we do have a medical blackout (which is the current law), so we're reduced to speculation.