We all know about the upcoming Spin offs and some characters return while there will be new ones but I'm focusing what Characters I hope will return for further character development.
Dave After what happened after the finale he needs to return for redemption from what I remeber from last season he didin't seem that Shawn would be caught in his crossfire when he tried to killed Sky. So what I hope is that they would take advantage of this meaner version of him until his elmination or so where Sky would explain herself to him and he would stop or something.
Sierra she needs to return so we can see a season of her without being near Cody or Cameron. So we can finally get some character devolpment outside of her creepy self.
Jo After her performance in All Stars she needs to return to try and compete some of the Atheltic contestants such the a couple from the 3rd gen (If Sky, Jasmine and Shawn count as worthy openents in her book) And some new contestants that some will maybe be good at physical challenges for her to compete against
Heather Now that there's a contestant that is a nicer version of herself in the form of Sky. Heather needs to return for this so I can see how'll she react with her.
Sky I hope she returns so can try to explain to Dave about what happened at finale without turning into Zoey. And I hope if both her and Heather are competing they would have some form of interaction.
Scott I hope returns in his All Stars self because it's one of the very few positives of Total Drama All Stars
Jasmine Since the spin off will maybe about going around the world I hope they do Austrilia because that's her home country
Shawn I hope returns but not be as delusional about zombies but will still have some because that's his character
Bridgette Since one of the new characters has the same voice actor as Bridgette she may or may not return as a contestant herself.
That's all I can think of right now sure I can say a few more but most have a less likely chance of returning but if can think of anything do it in the comments.