Better Call Saul's season 6 teaser which confirmed Walt and Jesse's return may have already offered a subtle hint as to how that will happen.
Better Call Saul operates largely as a prequel for Breaking Bad, following the titular Saul's past as Jimmy McGill while he becomes further involved in the criminal underworld. The show also explores Saul's future, depicted in black-and-white as "Gene," which is his cover identity following the events of Breaking Bad. While the fate of older "Gene" is still up in the air, it now seems apparent that the prequel storyline will be building towards Saul's partnership with Walt and Jesse.
Despite now being confirmed to appear, the exact nature of Walt and Jesse's role in Better Call Saul season 6 remains under wraps. That being said, the image used by Better Call Saul's Twitter to confirm their appearance in the show is quite telling. Fans of Breaking Bad will recognize that it's taken from a scene in the season 2 episode "Negro Y Azul," which is the episode right before Saul Goodman is formally introduced into the show. This means that Walt and Jesse's return will likely be set during Breaking Bad, just before they get involved with Saul.
Ultimately, Walt and Jesse's Better Call Saul cameos being set between Breaking Bad's "Negro y Azul" and "Better Call Saul" makes the most logical sense. After all, the two have never met or even heard of Saul Goodman before his debut in Breaking Bad, so doing it any other way that takes place before that would no doubt cause a lot of continuity issues. Therefore, while it may be disappointing for those who were expecting something more or a bit different, it nonetheless means that Better Call Saul season 6 will see a time jump towards the end that places Saul right where he needs to be when he crosses paths with the duo.
For now, viewers will just have to wait and see how Walt and Jesse's cameos in Better Call Saul season 6 will play out and whether they'll see more of them. While it's unlikely that Walt's role will expand beyond his cameo, it is technically possible that Jesse can cross paths with "Gene" in the future—although in that timeline, the man formerly known as Jesse Pinkman is likely still in Alaska. Until they appear, it's reassuring that the audience will get to see the beloved duo make their return to television after so long.