The Big Bang Theory has been renewed for two additional seasons on CBS. Original cast members Jim Parsons, Johnny Galecki, Kaley Cuoco, Simon Helberg and Kunal Nayyar have all renewed contracts for the next two years. It is said that Melissa Rauch and Mayim Bialik are still in negotiations.
If we had looked at the writing on the wall, I think we probably could have figured on at least one more season because they needed it so they could make an effective launch point for the projected Young Sheldon spin-off series.
The new series has a cast but no air date, and I don’t think filming has started. It is expected that the Young Sheldon will air directly after The Big Bang Theory.