walt obviously isnt going to wipe out everyone, that m60 is probably for graymatter. i dunno though, im sticking to the ricin suicide. maybe he eats or smokes the ricin then goes into graymatters headquarters with the m60, forces them to finally admit the company wouldn't be shit if he hadnt started it and they screwed him over, and thats why he was resorting to cooking for money in the first place. gets arrested, dies from ricin soon after. skylar gives up lydia, all hell breaks loose, montage of deaths all over