Not an entirely surprising Star Wars rumour.
The upcoming Rogue One: A Star Wars Story, directed by Gareth Edwards and starring Felicity Jones, is set prior to events in A New Hope. Therefore an appearance by Darth Vader wouldn't be unexpected.
The Sith Lord has already made his presence known in Star Wars Rebels on Disney XD and James Earl Jones is rumoured to reprise voice over duties on the big screen, too.
Rogue One: A Star Wars Story is released in cinemas 16th December.