Base rate of death within the next year for an 85 year old man (in the UK) is 10%.
There have been rumours about his health before (but he is almost 85...) so I wouldn't update too much based on that.
He surely has better healthcare than the average UK 85 year old, but I'd think even the best healthcare wouldn't more than half the probability. He probably also has slightly less chance of dying each year for genetic reasons.
There's a small chance (maybe 2%?) that he does not die but becomes incapacitated enough to force resignation.
I think risk of exile or other ousting is around the 1-2% mark, so in total I'd go for 10%.
Checking crowd activity after writing the above rationale, seems like @404_NOT_FOUND has come to a pretty similar conclusion with similar estimates for similar possibilities, but with a more detailed rationale which I broadly agree with. You might want to read that rationale for more.
One other scenario is that Iran is in the process of an organized transition to the next generation of leadership. I have no insight into how long that will take, but Khamenei has stacked the body that does that deliberation with his own people, and appears to want one of his sons to be the next leader. i.e. there's at least some chance of a peaceful and intentional transition of leadership in the next year.
IMO the crowd is too low.
Checking crowd activity after writing the above rationale, seems like @404_NOT_FOUND has come to a pretty similar conclusion with similar estimates for similar possibilities, but with a more detailed rationale which I broadly agree with. You might want to read that rationale for more.