I'm thinking the two henchmen placed the flowerpot by the pool to frame Walt, and then left while the neighbor lady was inside the house.
No. Remember last week, when Walt was spinning the gun? It pointed to him twice, and on the third spin...it pointed to the flower pot. That was how he got the idea. I couldn't believe it when people were suggesting that Walt had poisoned Brock, but it's true: he did it. He also sent his neighbor into a potential death trap. He also shot two of Gus's goons in cold blood. He also blew up Gus and Tyrus. I'm not sure how hard I can root for him next season, and I'll be interested to see what the hell they have planned for him. He still has further to fall, but, damn, he's pretty damn close to the transformation Gilligan promised from the beginning. I don't think he has any intent in "redeeming" Walt at this point, and with Gus gone, I think Walt will take his place as the actual antagonist.
And speaking of Gus...holy shit. About a minute before it happened, I realized what Walt's plan was, and I was practically hyperventilating waiting for the confirmation that I was right. And then when Gus walked out, I yelled at the screen, "HOW DID YOU SURVIVE THAT?!?!" But it was just an awesome death scene for an awesome character.