He was seen at the Pinewood Studios, where “The Last Jedi’s” shooting is happening. Could this mean he'll appear, like in the form of a Force ghost? I personally hope so, not like many other hardcore fans, I enjoyed AoC and RoS, especially RoS...
http://comicbooksgalaxy.com/hayden-christensens-comeback-in-star-wars-spotted-at-pinewood-studios/