I am starting to think that Walt saves Jesse in the end.
The ricin is for himself.
By the end of the final episode I believe that the following will have occurred:
1. Skyler, Marie and the kids have entered a witness protection program.
2. Walt still harbors ideas of reclaiming ‘His’ money from the Redneck Cartel(RC) to be used by his family.
3. Walt launches an assault on the RC compound with the intention of killing all of the RC and to also finish off Jesse.
4. Walt successfully kills the RC with the exception of Jesse. Walt is probably wounded in the shootout and is lying helpless in the compound. Jesse delivers the Coup de Grace to Walt but only after Walt makes Jesse promise that he will see that his family receives the bulk of the money remaining.
5. Jesse calls Saul one last time and makes arrangements with Saul to handle the details surrounding the money, with portions going to Brock and Walt’s family.
6. The last scene will show Jesse climbing into a vehicle and begin to slowly exit the compound with Walt’s body lying prominently in the foreground as the New Mexican sun is beginning to settle behind the mountains.
I have been thinking about the ricin being Walt's way out for a while now. And, I agree. Walt and Jesse's relationship is really complicated. Jesse simply couldn't handle the chaos anymore, especially after Todd killed the boy. But, Walt has always been very protective of Jesse. And, also jealous of him.
When Gus Fring asks Walt why he works with this "junkie", Walt simply replies that, "he does what I tell him". Soon after that Gus starts sending Jesse out with Mike, and I think he was trying to see if Walt is correct and Jesse does what he is told. I think Walt couldn't handle Jesse being involved with anyone but him. There were a lot of reasons to get rid of Fring; but, I have to wonder if one of them was Walt not liking Fring using Jesse for Fring's own purposes.
Jesse belongs to Walt; I'm sure there must be some psychological explanation for it.