Slightly off topic but I recently read that myself. I thought that's an odd thing for the producers to leave hanging out there. Something similar happened recently in Neighbours (a show I don't watch) but read an article how the writers were going to deal with the death of an old character, two years after the death of the actor.
But back to this topic. Considering the circumstances surrounding Larry's ill health and death the creative types of TNT Dallas decided they needed to kill off J.R. Was this a knee-jerk reaction? Possibly. Could they have continued with the series where JR is alive off-screen for a little while longer? Yes. Especially if the writers continued with the story JR had been searching for Pam for several months. Nothing like a good yarn involving two of the most iconic characters to breath life into this series. Missed opportunity.
They absolutely could have kept JR alive off screen for a while. I know because that's exactly what was done when Jim Davis died. The difference is that while keeping Jim Davis alive off screen served a purpose, keeping JR alive off screen would not have saved TNT Dallas from its inevitable fate.
Real Dallas did a wonderful job of keeping Jock a part of the storylines even when he was declared dead on Dallas. The best example is the way his memory was kept alive during the contest for Ewing Oil which was set up by the terms of Jocks will. That was brilliant! Even though Jock was dead, his memory loomed over Dallas heavily as both sons tried to continue earning his approval by striving to win the contest to each show Jock that his faith in each of them was well placed. Jock realized that control of Ewing Oil had to go to the best man for the job and that it would have been unfair to just gibe one of them control of the company without giving the other a chance to prove himself to be the most capable man for the job. Of course he ultimately wanted them to work together but had that not been possible, had the bus not been able to agree to do that, then only the most capable man for the job was deserving of becoming the man to follow in Jock's footsteps.
Realistically Jock could have pointed to Bobby quitting Ewing Oil when he had been given control of the company after JR had been shot. At first Bobby acted as if he didn't even want the prestigious position and acted as if he were just doing it as a favor to his parents. He showed his true feelings and motivations when he proved himself ruthless enough to renege on his agreement to only run Ewing Oil while JR was recovering from his gunshot wounds and actually used his brother's brush with death as a way to not only take control of the company but to then try to use JR's shooting as a way of permanently taking control of Ewing Oil away from JR. That showed how devious Bobby could be and that he would be a worthy adversary to JR in the future should they have to compete for control of the company. Bobby also expertly manipulated his mother's emotions into getting his way by threatening to take Pam and leave Southfork for good of Jock didn't give him power to run Ewing Oil as he saw fit.. He knew that would make Ellie advocate for him to Jock to allow Bobby to keep JR's job. That led to Jim Davis's finest single scene in Dallas when he gave Bobby the speech on "Real Power." "Nobody gives you power! Real power is something you take"! That scene can still give me goosebumps.
Despite all of Bobby's manipulations of his mother's emotions in order to get her to beg Jock to let Bobby keep JR' job long after JR had recovered from his wounds, despite Bobby originally saying he would only run Ewing Oil until JR recovered, ultimately Bobby found the stress of the job too much to take. He spoke of almost dong something he would have regretted (selling Brady out to Jeremy Wendell for the 15 million dollars Wendell agreed to give him as an incentive to make the deal with WestStar). He said words to the effect that he didn't ant any part of running Ewing Oil anymore because he hated being out in the middle of difficult situations such as the one between Brady's independent gas stations and WestStar, who were willing to offer more money for Bobby's oil than Brady did.
Jock could have referred to that in is will and said that Bobby displayed that he didn't have what was necessary to be the man in permanent control of Ewing Oil. Had he done that though, the viewers would have been deprived of seeing JR and Bobby in competition for the leadership of Ewing Oil during the contest made necessary by Jock's will. Seeing JR and Bobby in competition as per the stipulations of Jock's will was arguably the most exciting, long term storyline Dallas ever had!