Okay, I know you read the title and you are probably screaming a louder “Noooooo!” than when Luke found out Darth Vader was his father but save the vocal cords, this is just a rumor and nothing more…so far.
Making Star Wars has reported that they have heard that “a team in the U.K. are soon heading to the U.S. to begin training Hayden Christensen for a Star Wars: Episode VIII appearance of some sort.“
The site does also mention that even they have a hard time believing this rumor. Making Star Wars is trying to narrow down where the actor would exactly fit in with the upcoming Star Wars film slate, if the rumor proved to be true. Their guess is Rogue One or Episode VIII with flashback scenes.
Source: Making Star Wars