I wonder what they'll do at the end of next season, as Sheldon will be finishing up his senior year at East Texas Tech, and does his graduate studies at Cal Tech when he's 14, so he should be headed off to California at the end of season 7.
Personally I'd be fine if they just ship him off and concentrate on the rest of the family, as they're more interesting, though George dies while he's at Cal Tech, so that will be coming up as well.
So would make sense to end it with him graduating and preparing to move off, mentioning in the voice over at the end that his father passes away soon while getting a goodbye hug from George.
Have seen a few things written that the plan is to end it at 7 years, of course if CBS pays a boatload of money to Warner like they did for BBT, they might continue it, but I doubt it, show is CBS top rated, but ratings for BBT was massive compared to YS, does not deserve even close to the same payday.
Actors are a weird bunch also, after being on a show for so long, they get bored and want to do different things, if it was me, I would ride the train (show) to end of the line for how much they get paid.
I read that when the plan was to renew BBT for 2 more seasons, each of the main actors would of cleared $80-100 million for each season because of their per episode pay, syndicated and streaming deals, no wonder they were mad at Jim Parsons when he said no more.