TV Guide has gotten confirmation that Joseph Morgan's Originals character Klaus will be returning to The Vampire Diaries sometime in the future. The suspicion is that his return could happen in The Vampire Diaries' 100th episode next year, though representatives from the network and the studio did not comment to TV Guide about that.
You can read the TV Guide piece that broke this news here.
It is safe to say, though, that Morgan's return to the parent series will probably have something to do with a reunion with Caroline (Candice Accola).
Klaus first appeared on the parent show during its second season.
The Originals, a spin-off of The Vampire Diaries, has been a hit for The CW, with the latest Tuesday night Originals-Supernatural pairing giving the network their best Tuesday since 2008.