When last we saw Gendry, he was paddling off into the Narrow Sea - his destination unknown. Gendry was a major character throughout seasons 2 and 3 - and since George RR Martin hasn't found a way to brutally murder him yet, we can only assume he'll pop up later in the story (in order to be brutally murdered).
Theory: He's heading to Braavos, where he'll have a run in with his ol' m'lady, Arya Stark.
I had to take a phone call towards the end of the episode, so I may have missed something important, but the question remains: who killed the most powerful man in Westeros? This cliffhanger will probably be a mystery throughout the upcoming season.
Theory: Probably Jaime, in revenge of his younger brother Tyrion, who probably was executed while I was on the phone.
Something important was in the box being lowered onto a ship, overseen by Varys. Could it be that wizard dude who chopped off Varys' dick as a child (and whom Varys was keeping locked up in a chest)? Hopefully we'll find out soon next season.
Theory: It was Gendry, who - like Bran - can "warg" into different things. In this case, Gendry has warged into a crate.
Like, wait. How? I can't even come close enough to Google it and have Google know what I was getting at. Shit. This is why people just call her Kaleasy. Or Culleezee? GODDAMMIT.
Theory: D-U-H-N-N-ahhhhh fuck it whatever.
Ugh, he's in a hole and he's gonna hang out with this old tree guy. Great. Odds are this "flying" shit the guy's talking about is some metaphor too. Unless Bran starts literally soaring around Westeros, warging into dragons or something, let's hope the skeleton people find a way into that cave.
Theory: No, no one cares about Bran.
Like, Arya's pretty good at killing people. Maybe that's why she got on that ship at the end? Had to flee the country before word got out about Tywin's death? Then again, I think she was pretty far away from King's Landing. I can't really tell the geography of this world though.
Theory: Maybe it was Gendry? Yeah, probably Gendry.
Oberyn was awesome, right? And sure - it looked like The Mountain gouged out his eyes and exploded his skull, but...did he? That would be a hell of a twist, right? That Oberyn faked his death and was still alive and gonna do more cool stuff next season and okay maybe I just really don't want him to be dead, whatever, just let me have this.
Theory: He AND Joffrey faked their deaths, and now they're gonna team up to solve the murder of Tywin.
Oh wait, did we even consider this? Tywin's the ultimate schemer - he has a plan for EVERYTHING. He's basically the Batman of Westeros, except he doesn't fight crime and his kids fuck each other. Wouldn't it make sense that he would fake his own death? It's not like Tywin Lannister - the Lord of Casterly Rock - would allow someone to murder him on the toilet, right? Right.
Theory: Tywin, Oberyn, and Joffrey team up to track down Gendry before he reaches Donearos Denneeres blonde dragon lady.