Theories
I think that Dante (Jason Momoa) will be hired by Cipher to go after Jakob, if your remember at the end of F9, Dom told Jakob that there would be people trying to hunt him down.
Also if Gisele is returning, then I could see it being some rescue mission with Gisele being captured by Cipher and/or Dante, hence why Han came to visit Deckard at the end of F9 to help him rescue her.