walt knows he doesn't have long to live, the cancer is beating him.
he cooked up the idea of getting money to the family but having his son turn on him like that broke his heart and walt seems to give up by calling the dea and giving away his location.
then while waiting for the boys to pick him up he glances at the TV and what does he see? his oldest and most hated enemy, his old chemistry partner, this ignites a new fire in walt.
he's gonna take whatever cash he has and use it in one last ditch hail mary to take out the nazis, then when he finds out jessie is still alive... takes out jessie with ricin laced cigarette (wouldn't surprise me if walt gives it to him and jessie smokes it knowingly), he keeps todd around to help with taking out his old chemistry buddie but then finds out from skyler about the death threat, he then takes out todd.
hopefully marie gets killed somehow
show ends with walt tracking down his chemistry buddie and finding out he has taken in walt jr and secretly has been working with lydia (or getting ready too) AND the kicker will be that as walt is getting ready to kill his buddie and lydia, walt jr walks in and takes out walt.