All shipping aside, I really hope Ishida doesn’t kill off Touka. Not only would it be fridging her, but it would unnecessarily regress Kaneki’s character at this point. We all know Kaneki’s been through the ringer, but losing Touka after finding such hope in their relationship would slingshot him back to either the berserk Centipede (which is somewhat hinted at, and there’s an obvious parallel with Arata) or the suicidal Black Reaper, which would essentially move the plot in a aimless circle imo. I’m hoping she isn’t killed off as a plot device for Kaneki’s pain. We’ve already seen his volatile reactions to the death of a loved one. However, we all know Ishida loves to torture his characters so Touka being kidnapped and/or tortured is not off the table. Even though I wouldn’t want to see that either (poor Touka!), at least there would be a clear ambition to save her and could serve as a uniting arc for Black Goat, as well as paralleling Yamori’s torture.
Hope is essential for Kaneki’s development forward at this point. He’s lost all hope before and we know which direction his personality takes, so from a storytelling standpoint it would be poor writing to loop the plot back to one of Kaneki’s previous hopeless, toxic states. I don’t think he’d recover again after permanently losing both Hide and Touka and the plot would suffer in turn.