The character of Kai, who was the main protagonist at the beginning of season 6, has been dealt with, thanks to Bonnie who left him behind in the 1903 prison world that was previously inhabited by Mama Salvatore.
The last we saw of the character, Kai, the role essayed by Chris Wood, he was left at the mercy of a blood-thirsty vampire. It's assumed that Kai is still alive in the prison world as his Jo is still alive, and the prison worlds haven't collapsed yet.
But when will the character return? According to Internet Movie Database, Wood will be back for the 20th episode titled "I'd Leave My Happy Home For You," which will air on 30 April.
It is not immediately known how Kai escapes from the prison world, but rumours hint that Damon has a role to play in Kai's return to Mystic Falls, causing Bonnie to flip out. Ever since Bonnie's return from the 1994 prison world, she has become tougher and her main ambition was to kill Kai and make him realise the torture he put her through.
Therefore, Bonnie isn't going to be too pleased when she realises that Kai is alive.
Meanwhile, episode 20 is going to see Damon offering Elena the cure for vampirism and she turns to Bonnie and Jo for guidance. Their suggestions are going to throw up other interesting questions on Elena's future as a human.
The official synopsis of "I'd Leave My Happy Home For You" reads: "As Alaric and Jo reluctantly participate in their bachelor and bachelorette parties, Damon and Elena discuss the ramifications from an impulsive offer that Damon makes. Unsure of what to do, Elena turns to Bonnie and Jo for advice, but is left conflicted when Bonnie raises some unanticipated concerns. When Enzo realizes Lily is on a dangerous downward spiral, he asks Stefan to help intervene before it's too late. Lastly, fed up with the supernatural threats that plague their town, Matt takes his frustrations out on Tyler, while Alaric considers a life-changing piece of advice."
The episode is also going to see the return of Liv Parker, who was last seen in "The Day I Tried to Live."