The official companion book for The Force Awakens shows that J.J. Abrams wanted to use the hybrid Darth Vader Anakin Force Ghost in that first sequel, but the idea was abandoned.
Here is a description of the heartbreaking scene that finds Kylo Ren, Anakin and Darth Vader sharing the screen together.
And, SPOILER ALERT, it not only features Kylo Ren and Anakin Skywalker, it also features the return of Darth Vader.
Apparently, if we’re to believe the hype, there will be a heartbreaking scene in Star Wars 9.