I don't thinkwe willever really know for sure if Walt poisoned the kid or not, but we will always suspect that he did. And I doubt Jessie will ever find out, at least without a doubt, there will probably be another confrontation about it ion the next season. The plant was in Walt'sback yard, remember the scene when he spun the gun and it twice pointed to him? The third spin pointed to the poisonous plant.... I suspect in season five we will see Walt turning into a ruthless drug kingpin much like Gus who will go to even great lengths to protect what is dear to him. And,I think Walt willeventually tellHank about everything, Hank unknowingly is already too deep in, how will he ever explain how the biggest meth cook in the southwest was living right under his nose, his brother-in-law no less and he never knew. Walt has been paying his medical bills and expenses and Hank killing of the Salamanca boys will only look like he was helping Walt eliminate the competition so he could move up and take over their territory.
I also think a lot is left for the viewer to figure out. Like Skyler explaining to Walt why she gave Ted the $600K+ to protect them or how/if she found out about Ted breaking his neck, you know she will think the two guys Saul sent done it and it was no accident. My question is will she feel responsible or think Walt had him killed? After all "He's not afraid of a knock on his door, he's the one knocking on the door" and after the season four finally he's proved it killing Leonel Salamanca, Gus and Victor with a pipe bomb. I'm also wondering just how Skyler will react to the bombing? Will she try and leave Walt again in fear of him or maybe become more involved in Walt's "business" I could see her becoming very conniving and ruthless herself. With Gus and the major Cartel players now gone I look for Walt to become the new "boss" at least for a short time if he can get Mike on board. Mike knows all of Gus's operations, collections and distributions, and Walt is showing he has the smarts to control things, somewhat. And if he does bring Hank into it then he has a mole inside the DEA. I haven't thought about Walt's cancer coming back though, that could be a real twist of fate. If Walt gets his family more involved in his meth business and then gets a grave prognosis about his cancer. He could be left to watch as his wife, brother-in-law, Jessie and maybe even Walt, Jr get in over their head as a result of his actions and be able to do little about it.
This show is all about actions and concequences. How would Walt ever think that watching Jane die would have led to the plane crash? Or his idea to make a little quick cash for his family would have him becoming the criminal he is now, remember how Hank described Heisenberger early in the series, as a new heavy weight player in the meth business? What will be the concequences of his actions in the upcoming season?