Yes I can see how Walt not being in the next episode would make us think.
They did say that Vince Gilligan was going to tie up all loose ends, so I was hoping that they would show us How Gus Fring became to be the king of meth, that is a loose end for me.
I hope to see more of badger and his mate as well, maybe they will go on the hunt for Jesse.
The lipstick thing I agree it might mot be significant or it may play a big part (like the rug that Beneke fell over) maybe Todd will pretend Lydia has been there by just placing the mug on the desk, or Walt thinks that she is there I don't know.
Early on in the episode we saw Walt going back to his derelict house and the words Heisenberg were daubed on the wall, I thought either Hank or Walt had done that, and now Hank is dead I think Walt does it.
I think with all the theories that are flying about, the one thing that throws everyone is who is the ricin for? After all he has got a big gun and not a lot of time, he doesn't need to poison anybody he can shoot them, so maybe it is for him.