In an interview given with The Mirror, David Prowse, the man inside Darth Vader’s costume, revealed that he has dementia. He commented that he would have loved to have been a part of the films, but he worried that he would have forgotten his lines.
He does tell The Mirror that “I would have loved to have done something in it – even if it was just a cameo.” This, I believe, confirms that Prowse will not be seen in Episode VII.
Dementia is a disease that is difficult to live with, both for the patient and for their families. Please keep David in your thoughts and prayers.