Before Sunday's episode I had the following theories about the ricin and the M60
Theory 1: Lydia and Meth Damon can not meet the high standard required by their foreign customers, so they try to get Walt back as a cool. The White's are exposed and Walter (and potentially the whole family) go into hiding, making them unreachable. Lydia and Meth Damon instead turn their efforts towards Jesse, kidnapping him and forcing them him to cook for them. Walter needs the M60 to take out most of the gang until he is left with a few key players, when he will then trade himself for Jesse's freedom. The trade happens, Jesse is freed, and the DEA shows up after the fact to arrest whoever is left after a tip off from Walt. Little does anyone know, but Walt had taken the ricin before his assault, thereby insuring he was removed from the equation no matter who captured him.
Theory 2: Jesse is going to testify against Walt, and the location of the money has been lost. The ricin is for Jesse and the M60 is for Lydia's gang so he can rebuild his empire.
I was happy to believe theory 1 was the direction the show was going (and I'd still be happy if it went that way), but after Sunday I wish I pushed the second theory. I can see Jesse setting the house on fire, but it getting put out before getting too big (maybe Walt Jr walks in just as Jesse throws a match down and Jesse helps him put it out with a house hold fire extinguisher?), but bad enough to force the Whites out and bad enough to burn up the lotto ticket. From Talking Bad we know the Whites take a staycation next episode. If they were hiding from Jesse or Hank I would imagine they would skip town, so is it a fire or is the gas smell enough to force them out?
Who knows, though I do get the feeling that if this fire does not happen, it will because Jesse and Walter Jr. have finally met.