What would be some storylines? IMHO they would drag on Penny being pregnant right until the end of the season, just like Lorre did with Shamy's wedding and their Nobel Prize
They never had Raj in a happy relationship and that wouldn’t change in Season 13
Sheldon despite his Nobel Prize speech would revert to his old ways. Amy tricks him into having a baby.
Bernadette would continue to belittle Howard and they divorce.
Barry Kripke would be named the chairman of the Physics department
Leonard and Penny would buy a house in the country. Leonard will become a high school physics teacher: Penny hates country life.
Stuart and Denise get married and at the end of Season 13 they are the only ones happy.
What do you think?