I'm hopeful they keep the Hound (Rory McCann is one of my favorite actors on the show), but with his plot, I do think he either has to die or has to be taken out of action for a season. Not only because they're going to have to shift to so many new plots to not completely outpace the books (Dorne, the Citadel, Jon…

I don't think either had any real face-to-face interaction with him, and if I recall they saw the Gravedigger from a distance. Although I'm sure the Hound has a pretty distinctive physique, GRRM could present that he lost weight, was hunched, somewhat crippled from his injury, etc.

My thought for the larger purpose has always been just to defeat Robert Strong at some later point (and similarly that either Robert Strong will win the trial by combat or the High Septon will call the gravedigger as his champion), so the Hound can defeat his brother.

He's the only one of Cersei's Council that's made an appearance, which is reason enough to emphasize him in my opinion, although his disgraced maestar status has hardly been invoked at all. I think they'll keep the Blue Bard and Stokesworth plots to display Cersei's madness and Qyburn's complicity, but they can still…

I strongly suspect—based, in part, on the show's aversion to characters having secret identities—that the Mountain and the Hound will both die this season and the grave digger and Robert Strong will be written out. Certainly Qyburn could create some other Frankenstein's monster-esque creature without viewers knowing…