I'm glad that Caitlin retained her metahuman powers. I hope they do something interesting with her next season. I presume that she's still a wanted woman for kidnapping Julian, so she'll have to operate out of the limelight. An anti heroine who reluctantly assists Team Flash from time to time would be good to see. And maybe they can give her an independent storyline, but I'm not sure what. I suppose she could try to hunt down Ronnie, but I'm tired of her storylines revolving around men. Maybe she could try to get her mother's energy generator invention thin up and running, ostensibly to sell to the highest bidder on the back market but she eventually has a change of heart and publicly shares her research / findings for the betterment of mankind?
Or maybe she roams the streets of Central City helping to defend citizens on a smaller scale - stopping thugs, but then robbing the thugs to pay for her own bills (those leather miniskirts and thigh high boots can't be cheap).
I think the cast needs to be seriously downsized. They can't have four speedsters on speed dial. Wally, Jesse and Jay all need to be written out. Not necessarily permanently, but they can't just pop in and out for no real rhyme or reason. They detract from Barry and make it implausible that Team Flash can't easily stop the majority of their villains. It's frustrating enough that Barry only remembers certain skills in limited episodes.
Barry needs to be happier and more optimistic like his season 1 self. And he needs to be less of an idiot. Barry and Iris shouldn't have any relationship drama and Iris needs an independent storyline. Future newspaper or not, maybe she should become a police officer since it would get her more involved with the storylines and her journalism career isn't really contributing to the series. Cisco has access to more research and information that Iris does at the newspaper.
Cisco definitely needs to return to his happy, pop culture referencing, geeky self.
I'd be happy for Harry to recur, but a season without a permanent Wells would be refreshing. Tracy Coull help to fill the void or they could always get Dr McGee to appear as well in an older mentor role. And the Pied Piper is still out there somewhere as a powerfully and brilliant ally.