Through Breaking Bad, we do have some of an idea how things shake out for Jimmy as this series ends and Walter White takes center stage. Chuck told Jimmy that his actions always end up hurting people and that he’ll end up dying alone. Of course, this turned out to be foreshadowing for Chuck himself, but given what we know about Jimmy in Omaha, we may not have to look that far ahead to see Chuck was right. For Jimmy to become Saul, the right circumstances need to present themselves at the right moment with the right nature/nurture mixture. We’ve seen that in Chuck’s suicide, but for it to stick – for Jimmy to embrace Saul and to never look back from it – he needs to lose Kim.
While Jimmy is self-aware enough to recognize when he’s done something wrong - and even show regret and make amends - Kim and Chuck have always been his moral compass, keeping him right at the line of criminal behavior. Alone, we already know that he goes from being a criminal lawyer to a criminal and a lawyer. We know Jimmy will need a catalyst to embrace becoming Saul Goodman fully. Kim and Chuck have held him back from that. Kim herself has a complicated relationship with Jimmy’s morally ambiguous actions. For her, the limit does seem to be the occasional grift on an obnoxious bar patron. She wouldn’t stand for the actions Saul takes during the Breaking Bad series, which are definitely beyond the things that Jimmy is doing right now.
Of course, there’s another route to take as well - one where, similar to Walt, Jimmy makes it impossible for people to be around him. He might become Saul out of necessity. His law license is suspended, his Sandpiper check is still years away, and Kim is on sabbatical following her car accident. Even when he gets his license back, Elder law is clearly no longer a viable option for him, so he’ll probably return to public defender work. From Breaking Bad we already know that Jimmy has some tangential connections to the cartel through Mike (Jonathan Banks). It’s possible that in the interim, he'll take on an advisory role in Gus Fring’s (Giancarlo Esposito) still-growing empire. This, of course, harkens back to one of the main themes of Breaking Bad: the desire to provide and thrive. If he wants to help Kim the way she helped him, Jimmy will have to go down a road parallel to Walter White’s. And that’s where the final tragedy can come into play.
Jimmy begins defending cartel members and is well compensated. The cases get bigger, darker, and the criminals’ actions more depraved. Kim eventually has enough, but Jimmy has no choice but to continue because, well, it’s the cartel. You’re going to tell them no? Kim leaves him and with no chance of reconciling. Either because of Chuck’s suicide or some new kind of malfeasance, Jimmy decides to distance himself from the McGill name. Maybe by now, he’s no longer indebted to the cartel, but he has no one to share this wealth and good fortune with. He wants to contact Kim, but there’s no way she’d give him another chance. He’s damaged their relationship too much with his poor decisions and the crimes he’s either committed or abetted; after all, now he has a solid reputation among the criminal element, so he just goes and embraces the Saul Goodman shtick because, as Chuck said, “Why bother?” Why bother trying to fight it?