Spoilers ahead for the Season 6 finale of The Flash on The CW, called "Success Is Assured."
The sixth season of The Flash has come to an end, although not quite the ending that was originally intended. Production shutdowns forced Season 6 to end three episodes short of its 22-episode order, so the cliffhangers that "Success Is Assured" ended on weren't meant to hold fans over into a hiatus. Admittedly, Iris seemingly being consumed by the Mirrorverse isn't a bad cliffhanger to end on, and Sue Dearbon being framed for murder is a decent hook, but I'm left hoping for one thing above all others in Season 7: Dark Barry.
For the first time in Flash history, a season actually ended with the villain winning and Team Flash pretty spectacularly failing. The heroes weren't able to stop Eva from murdering Carver, and she impaled him with shards of mirror. Iris and Kamilla are still stuck in the Mirrorverse, and Barry basically flat-out told Nash that he's willing to cross lines now because Iris is his wife.
Barry even considered a deal from Mirrorverse Singh on Eva's behalf that would involve trading Carver for Iris. While Carver would probably be the big bad of the second half of Season 6 if Eva hadn't gone ahead and managed to eclipse him in the evil department, making a deal with her wouldn't be the heroic thing to do. It would be pretty understandable and arguably even romantic, although even Barry knows Iris wouldn't want to be rescued because he traded a life for hers.
That Barry considered the deal at all was enough to alarm Nash and the various versions of Wells in his head. The Thawne version of Wells even said that his version of Barry never would have done that. Since Barry pretty clearly hasn't been replaced a la Iris, Kamilla, and Singh, fans can probably take this as a sign that even The Flash's original baddie doesn't recognize him as the hero he once was.
Between Barry actually losing the fight of Season 6, being unable to recover his wife, and his surprising self-awareness that the rules don't all apply for him when it comes to Iris, I think a Dark Barry twist would make sense and could really work. It's also something that The Flash hasn't explored for Barry on an ongoing basis, and The Flash could use some new ground to cover.
I'm not saying that The Flash needs to become Arrow 2.0 and fully embrace the doom and gloom, but I'm definitely hoping for The Flash not to reset itself once the good guys inevitably come out on top. Grant Gustin could have something new to do, and it would seriously make sense for Barry to take a turn for the grimmer for at least a while in Season 7.
He went from losing his mentor and friend in "Crisis on Infinite Earths" to dealing with post-"Crisis" changes to losing Iris. No matter how touching Caitlin's speech about Barry's capacity to love may have been, I'd like to see some fallout beyond Barry finding speed and direction again because of his good heart.
All of this said, I might have been singing a different tune if The Flash hadn't had to end Season 6 on "Success Is Assured," since Team Flash might have beaten Eva, recovered Iris, and tied off the loose ends in time for another happy ending. With Season 6 ending on "Success Is Assured," though, I hope that The Flash takes takes Barry in a darker direction for at least part of Season 7. That doesn't mean Grant Gustin can't get his updated suit!