Because of The Big Bang Theory, it is known that George Senior dies when Sheldon is fourteen. While the actor, Iain Armitage, is fourteen in real life, the writers of the hit prequel have kept his age in the show closer to 12 for season 6. It is clear that they are trying to delay telling the inevitable story of killing off George Sr., as his character's death would shift the show's dynamic completely. But Season 7 is likely when the event will occur, as Sheldon will be fourteen by then, keeping with the original timeline.
Since Sheldon is only twelve now, the network faces an actor problem as Iain Armitage ages. He will turn 15 in 2023, which means that heavier storylines, such as George's death, have been put off long enough, and they cannot delay it too much longer. In the Young Sheldon universe, George has had heart problems for years, as well as a significant drinking problem that is brought up in TBBT. It is unknown if he will die due to a heart attack or alcohol-related issues, but the writers will likely have only one more season to set up his death.
Another reason his death is unlikely to occur in the present Season 6 is that one final storyline must be tackled. Also, keeping with TBBT canon, Sheldon catches George cheating with another woman when he is 13, with his father's death occurring a year later. It is safe to assume that this woman will be Brenda since their relationship has been featured and teased over the past couple of seasons. While Sheldon's age hasn't been stated explicitly in Season 6 yet, the following episodes may confirm an upcoming birthday to solidify him as 13 and then present George's cheating scandal.
Since CBS hasn't renewed Young Sheldon for Season 8, the sitcom may be coming to an end. If Season 6 does dive into George's cheating with Brenda and Sheldon catching them, it will set up Season 7 for a much more serious tone. Season 7 will likely feature Mandy having her baby but George Sr. dying, a bittersweet ending to Young Sheldon.