Characters that we would expect to appear

*Dominic Toretto (Vin Diesel): No brainer
*Letty Ortiz (Michelle Rodriguez)
*Mia Toretto (Jordana Brewster)
*Roman Pearce (Tyrese Gibson): Will obviously make it out alive in 9
*Tej Parker (Ludacris): Will obviously make out alive in 9
*Ramsey (Nathalie Emmanuel)
*Han (Sung Kang)
*Sean Boswell (Lucas Black): Has signed for one more movie after 9
*Luke Hobbs (Dwayne Johnson): His story with Toretto have not ended
*Deckard Shaw (Jason Statham): WeGotThisCovered have said that he will be back, but I'd say it's not 100% a done deal, a lots to be resolved for Mr. Shaw, Han and also Cipher.
*Gisele (Gal Gadot): It's possible and WeGotThisCovered have said that Gisele coming back is a possibility for Fast 10.
*Jakob Toretto (John Cena): John Cena himself has been dropping hints that he'll be back, would be game to see him and Hobbs either clash or team up.
*Mr. Nobody (Kurt Russell): We've last seen him in 8, and he could return to help the team
*Little Nobody (Scott Eastwood): Hopefully he'll show up in 10 like his mentor
*Owen Shaw (Luke Evans): The door has been open for Owen to return says David Leitch
*Magdelene "Queenie" Shaw (Helen Mirren): The whole Shaw family must get together
*Hattie Shaw (Vanessa Kirby): Same reason for Queenie
*Twinkie (Shad Moss/Bow Wow): He'll return for 9 and no doubt he'll show up in 10 along with his buddy Sean.
*Cipher (Charlize Theron): No doubt sh'll appear in the final instalment of the saga

Possible
*Jonah Hobbs (Cliff Curtis)
*Mateo Hobbs (Roman Reigns)
*The Director of Etheon: Etheon was introduced in H&S and I'll say it will have some sort of role in F9.
*Agent Locke (Ryan Reynolds)
*Dinkley (Kevin Hart)
*Madam M (Eiza Gonzales)