I feel like he has to escape. There was never any explanation as is his immortality, but then again Kakuzu said there was no such thing as true immortality so maybe his jutsu will wear off and he'll die. Maybe his ritual take the remaining years from the people he kills and gives them to him. So in 1000, no let's make it 3000 years just to be safe, we'll go dig him up and see if he's still talking smack lol.