I had always thought that Harrison Ford wanted out of the whole Star Wars franchise and this Star Wars - The Force Awakens was going to be his swan song. It stemmed from hearing that Harrison wanted his character to die at the end of Star Wars VI - Return of the Jedi which never happened. Well, according to IMDB, on their Episode VIII page, they've listed Harrison Ford as being one of the cast members. Whilst there is mention for Luke Skywalker, the other main characters aren't there in the list. It remains to be seen if any of the other characters such as Chewbacca or Princess Leia will return. The news of the all important new female lead character who'll join Rey and Finn against the First Order is eagerly awaited.
*SPOILER* Of what I have heard whether rightly or wrongly that a major character will die off. If I were a betting man I would put my money on a certain hairy character rather than anyone of the others given how old the actor in the suit is. For the droids, the people inside could be replaced by someone else as we don't see their faces ever. As for C-3PO voice, it could be adjusted and a plausible reason given why the accent has changed. Whoever it is, he'll be missed by the many star War fans out there.