I don't think he was in Yashahime(Inuyasha sequel) so probably not a sudden death.
He was.
He came back to reprise his role, but I guess he only got 2 or 3 episodes in (however far in advance they record) before dying. He was definitely in episode 1 when I watched it a week or so ago. He sounded really off, though, so I guess he's been sick for a while.