A part of me is really hoping that Season 4 goes through a huge revamp and revives the show in a similar way that Arrow did with its current season.
And one thing is for sure, aside from the crazed Tumblr fans, almost everyone thinks that Iris is a useless character. Either kill her off or take her off the show for awhile until they come up with something for her to do that seems realistic and would contribute to the story without adding forced drama.
That would be nice, not killing Iris off, though I agree that she is a very unnecessary character right now, but shaking the show up. I would love for it to actually focus more on its title character, I like the group but they are really a problem when it comes to have Barry grow as a character since they hold him back to do just that - at least in the current writers' hands.
It would be nice for Cisco and co to either move or focus on their own lives more, still making cameos but not being there every time something goes wrong.
Same goes for Wally, I think they made the mistake to introduce him way too early, Barry is by no means able to stand on his own yet, he can't be a believable mentor not matter how much they try to push that on us.
Caitlin is a character I really started out liking but over the last two seasons I became totally indifferent to her, if she would be written off the show I could really care no less. The whole Killer Frost thing is ridiculous, and, again, just to invent new drama.
Iris is someone I don't want to go, because I love Iris and Barry's relationship in the comics (the preNew52 ones), and I would love to see them as that kind of couple, but right now she really only drags the show down for me, she offers hardly anything, she had done nothing significant or helpful so far, and while I have no problem with the actress, the writers really give her nothing to do other than standing there, look nice, and cry every once in a while. It is utterly frustrating.