Alaric (Matt Davis) from "The Vampire Diaries" will crossover to "The Originals" to meet with Elijah (Daniel Gillies). Meanwhile, Klaus (Joseph Morgan) might end up with his one true love, Caroline (Candice King).
The executive producer of both "The Vampire Diaries" and its spin-off series "The Originals" – Julie Plec – likes to intertwine the storylines of the two shows. In season 1 of "The Originals," Tyler (Michael Trevino) from Mystic Falls came to New Orleans to get revenge on Klaus.
In "The Originals" season 3, Matt (Zach Roerig) and Stefan (Paul Wesley) appeared to attend to their own business in New Orleans.
In "The Originals" season 4, TV Line confirms that Alaric will be crossing over to New Orleans to meet with Elijah. He will be bringing an artifact to the eldest Mikaelson sibling, but the purpose of this artifact is still unknown.
Meanwhile, there are speculations that Klaus will have his happy ending with Caroline in "The Originals."
In "The Vampire Diaries," Stefan and Caroline are already engaged. But it seems that with where the show is heading, it is possible that something bad will happen to Stefan and will cut his happy engagement off with Caroline. Even Wesley — who plays Stefan — has predicted that he might be killed off in the final season of the series.
In "The Originals," Cami (Leah Pipes) was Klaus' other half but she was killed off in season 3.
With both Stefan and Cami gone, Klaus and Caroline have a chance to start over and renew their relationship. And now that "The Vampire Diaries" ending soon, the character of Caroline can be brought over to "The Originals" to continue her romance with Klaus. But there has been no confirmation of where the storylines of these characters are going.
Meanwhile, there will be newcomers upon the return of "The Originals" next year. Christina Moses from "Containment" will appear as the werewolf doctor named Keelin and "Sleepy Hollow" actor Neil Jackson will play a vampire named Alistair.
"The Originals" season 4 premieres on March 17, 2017 on The CW.