There is some recycled dialog in the second teaser for The Force Awakens, with a voiceover by Luke:
The force runs strong in my family. My father has it…
Assuming that the dialog is from The Force Awakens and not just lifted from Return of the Jedi, it implies Anakin is still present. He was seen as a force ghost at the end of Jedi. So conceivably could still be around.
But someone would need to play him. Have there been any rumors about this?