Better Call Saul needs to explain why Kim Wexler (Rhea Seehorn) isn't in Breaking Bad, and one way to do that is for Jimmy McGill (Bob Odenkirk) to arrange her disappearance with Ed Galbraith (Robert Forster). With Jimmy's ultimate fate known, and likewise those of Mike Ehrmantraut (Jonathan Banks) and Gus Fring (Giancarlo Esposito), Kim is Better Call Saul's biggest - and most worrying - question mark. The moral center of Jimmy's life (albeit a sometimes complicated one), fans have long been concerned that Kim's absence from Breaking Bad means her death.
It's possible that the show will go that route, and Better Call Saul season 5 has certainly set it up. Kim is in the game now, thanks to her marriage to Jimmy and interactions with Lalo, with the latter in particular putting her in the crosshairs and ratcheting up the tension as to what will happen to her. Kim dying at the hands of the cartel, and Jimmy being at least partially culpable in that, is an easy way for Vince Gilligan and Peter Gould to write Kim out of Breaking Bad and at the same time explain why Saul is who he is and never mentions her. However, there is another, more appealing option, especially for those who don't want Kim to be killed off.
Rather than Kim being killed off, it could be that she's made to disappear by Ed. Known as the Disappearer, Ed is a vacuum repair man who also helps people escape to new lives with new identities. This would fit with what Kim may end up needing right now: for as long as she's with Jimmy, there's going to be a target on her back (Better Call Saul season 5, episode 9 even made this rather literal). She won't want to leave, of course, but at some point there may not be much of a choice, especially if Lalo remains on the loose and things with the cartel escalate. It's the kind of move Mike would encourage, and would also go along with in order to protect Kim. Getting her out of there thanks to Ed means she gets to live, but is still heartbreaking for both characters.
What makes this ending for Kim so appealing - aside from the fact that it means she gets to live - is that it mirrors the ending for Saul in Breaking Bad, where he becomes Gene. Gene's life already seems somewhat sad, but knowing that it's the same fate that befell the woman he loved makes it all the more poetically tragic. It also gives the Breaking Bad universe as a whole a great sense of symmetry: Better Call Saul ends Kim's story with Ed making her disappear, just like Breaking Bad did with Saul, and El Camino: A Breaking Bad Movie did for Jesse Pinkman.
As well as giving Kim a bittersweet ending - which is at least more deserved than a brutal death for such a great character - this can also explain yet another Breaking Bad connection: how Saul knows Ed in the first place. These are the kinds of gaps Better Call Saul has enjoyed filling in, so it fits with that approach, and him finding him through the criminal underworld (or perhaps through Mike himself) here would work.
The sad note to this is Forster's passing, which likely rules out an actual appearance from him, barring footage that could be re-purposed from Breaking Bad or El Camino. However, there's an in-story explanation for that since, until Breaking Bad season 5, Saul didn't know what Ed looked like. That means they can still reference his character, and instead just use the Best Quality Vacuum repair shop or van to clue viewers in. It allows the show to use a great character one final time, clears up a number of Breaking Bad gaps, and gives Kim a more fitting send-off, whether it's something that happens in the forthcoming season 5 finale or, more likely now, Better Call Saul's sixth and final season.