If you watched BB you know that the two main characters sort of get happy endings.
Jesse sees his girlfriend get murdered, he gets tortured, and he leaves behind a trail of mayhem (drug overdoses, Gail, his family). But he escapes to Alaska with decent money and sees no jail time for his life of crime and mania. He thinks of Jane instead of Andrea even so he is over her death already and gets to live a peaceful life in his preferred location. Walt gets the same. His son hates him, Marie hates him, his daughter will probably hate him. But Walt's family gets millions of dollars and his wife will make sure of that, Walt gets to kill every single enemy he basically ever had in the drug game including Gus, Mike, the Nazis, and even Lydia, he frees his former protege, he gets to terrorize his old college enemies the Schwarz couple and force them to launder his drug money under the guise of "I helped build your company", and Walt dies without anyone knowing his blue meth formula, and he dies on his own terms instead of cancer or prison. All in all they did not really pay for their crimes. People like Hank or Mike pay for them instead.
Saul and Kim will get a similar happy ending. Everyone around them will get ruined like Hank, Howard, Nacho, Mike, Marie, Chuck, and so on. But they will emerge relatively victorious. This is how Vince Gilligan likes to write his favorite characters. He is like GRRM of A Song of Ice and Fire in that his main characters are fully plot-armored and everyone else dies no matter what. Midgets survive combat, a little girl destroys entire cities and hordes of bloodriders, a bastard comes back to life after actually being dead (despite the author saying that Gandalf coming back to life was poor writing).
Walt and Jesse reunited at the end of BB. Not under the best of circumstance mind you. But they were together at the end (of Walt's life). Kim and Jimmy will reunite. Almost assuredly as Gene and Giselle. The sinister cab driver is likely a friend of Kim or some type of impetus for Jimmy to seek out Kim and come clean to the world that he is a drug lawyer in hiding from a killer group of cartel experts. Jimmy can offer the DEA information on all sorts of stuff that they might now know about Lalo, Hector, Nacho, Gus, Mike, Walt, Jesse, and others. He might get prison and release or witness protection. And Kim's freedom can be part of the bargain.
But I doubt that Vince Gillian will do a Sopranos, Shield, OZ, Boardwalk Empire, ending where the characters are basically doomed or dead. Just as Walt came back with a vengeance and saved Jesse. Jimmy will come back and save Kim. "You don't save me....I save me". This time Jimmy will save them. But unlike Walt who died....only 'Saul' or 'Gene' will die. Jimmy will live on.
This seems very telegraphed to me and I would be surprised at an ending that is even partially different.