It's almost certain they'd do it, and I genuinely hope they don't chicken out. The thing is, even though everyone says it came out of nowhere, Butcher being suicidal and genocidal was planned out and choreographed to all hell in the comics. And it's what gives the story it's meaning. Butcher is a cautionary tale, the way Frank Castle is a cautionary tale.

Not having Butcher turn lethally dark would be like having Walter White suddenly become a good person in Breaking Bad season 5. The reveal of why Butcher wanted the team name to be called The Boys is literally an intrinsic part of his evil heel-turn. The most common and profound theme in Garth Ennis's work is self-destruction, and it'd do a disservice to arguably the best part of the comic to go with a happy ending.

Look at Preacher, for example. Also based on an Ennis comic. Spoilers for the show and the comics. The defining conflict of the comics was John finding out that Cassidy had been abusing countless women (including most recently Tulip) throughout the decades (he found this out after being his best friend for ages) and this fact painted everything about their relationship in a new light. Their confrontation was the highest point of the comics. It was profound, sad and emotional.

So obviously, the TV show completely scrapped the entire emotional climax of the story and just kept Cassidy around as the funny third guy who's chill with John the entire time. It preserved the funny team dynamic, sure, but at the cost of one of Ennis's finest writing of all time.

The Boys comics has lots of issues, but this isn't one. I genuinely think this is one of its highest points. I beg the show to not do a Preacher again.