I doubt it. Throughout most of Season 4 DVD, they are clearly working around Jim Davis' illness, not knowing what he can physically do or how long he will be around. He only looks close to 100% in the first 2 episodes of the season, perhaps a couple more. After that, his appearance and voice starts subtly changing, the confident Jock Ewing demeanour declines, and later on he is sitting down a lot. Jim Davis seemed to put every last ounce of acting ability that he had left into that scene where Jock and Miss Ellie make up. He only had one more appearance after that, sat down in a car as Jock and Miss Ellie leave Southfork.