Okay what I mentioned on that last page, about Walt going after Todd and that being the final showdown with the ricin... It all seems a little weak. I also mentioned, Todd is the only threat, knowing how to make Walt's perfect batch, because something is going to happen to Jesse... and that something is....
Todd, the emotionless gunman, is going to kill Jesse. Jesse will get in his way one way or another and Todd's going to take him out, forcing Walt to move to New Hampshire and then finally coming back to kill Todd and his uncle goon squad to finally end his batch and return to normal life. This is my theory.
So... a final showdown between Walt and Todd would mean so much more if Todd kills Jesse and Walt wants to erase involvement altogether. All speculation of course.