Natalie Portman will not be back for Thor: Ragnarok or any other Marvel movie.
Portman, who played Jane Foster in the Thor movies, filled in WSJ.
"As far as I know I'm done," Portman said. "I mean I don't know if maybe one day they'll ask for an Avengers 7 or whatever, I have no idea, but as far as I know I'm done. That was, all a great thing to be a part of."
Thor: Ragnarok has a new female lead with Tessa Thompson as Valkyrie.
Regarding Natalie Portman, there was said to be contention between her and Marvel while Thor 2 was filming. Reportedly, Portman was good friends with Patty Jenkins, the original Thor: The Dark World director, and Portman wasn't happy when Jenkins was let go. It was even said Portman was forced back to do Thor 2, but didn't want to return. Who knows? Maybe with Patty Jenkins directing Wonder Woman, there's a place for Natalie Portman over at DC.
"Thor: Raganarok" has a November 3, 2017 release directed by Taika Waititi starring Chris Hemsworth as Thor, Mark Ruffalo as Hulk/Banner, Tom Hiddleston as Loki, Idris Elba as Heimdall, Cate Blanchett as Hela, Tessa Thompson as Valkyrie, Jeff Goldblum as Grandmaster and Anthony Hopkins as Odin.