Vader had sacrificed himself to save his son Luke Skywalker but that should not stop Disney/Lucasfilm from bringing him back because "he's an integral part of the franchise."
"Replacing him is virtually impossible. The plan is for him to return and play a significant role in the new films. This is science fiction remember. Darth Vader will rise from the ashes."
The masked character has been portrayed by different actors previously. They included David Prowse who played Vader in the original trilogy. In the prequels, the character was portrayed by Hayden Christensen.
Scheduled to release sometime in 2015, "Star Wars Episode 7" has already tapped Oscar winner Michael Ardnt as its screenwriter. The project is still looking for a director.
While story is being kept under wraps, Mark Hamill, Harrison Ford and Carrie Fisher have all expressed their interests to return as Luke, Han Solo and Princess Leia respectively.