Will there be another season of Young Sheldon?
Yes. CBS has already renewed the show for a second season.
In January 2018, CBS announced that it had ordered a second season of Young Sheldon which will air in 2018/19. This was the network's first renewal of the 2017/18 season.
When will the next season air?
In the 2018/19 season.
CBS will announce its fall line-up for 2018/19 in May 2018. In January 2018 it was announced that the FOX network had won the bidding for rights to air Thursday Night Football from the 2018 season, replacing CBS and NBC as the current rights holders. This should mean CBS won't need to delay its Thursday night comedy line-up until later in the fall, as it has done in recent years.
What about the current season?
It is airing now.
CBS is currently airing the first season of Young Sheldon. The first season will contain twenty-two episodes and will air until May 2018.
Will there be a third season of Young Sheldon?
It is too early to say.
CBS is unlikely to make a decision on the future of Young Sheldon until the second season, which has already been ordered, has started airing.
A decision could come between January 2019 and May 2019, when the network will present its schedule for the 2019/20 season.