Call me a spoilsport, but I'd actually prefer to have no Kenobi story. I like the idea that between RotS and ANH, Ben Kenobi was just there, sitting on Tatooine, biding his time. Yeah, doesn't seem grand and spectacular and exciting, does it? But life is like that sometimes. Often, actually. And I consider it authentic for Obi-Wan's life to have a period of, well, nothingness in it, when all seems lost and dark, until the time of ANH comes.
Besides, we all know how a movie like that would go. It would feature an opening with Ben in the desert, showing his boring daily routine, with long silent sequences with melancholic music while he does his solitary hermit business, with close-up shots of various war relics, possibly a few flashbacks to what happened in the prequels, especially when he is touching / looking at what once was Anakin Skywalker's lightsaber (cue echo-like sound of Vader's iconic breathing noise in the background when Obi-Wan looks down on the floor, shaken by the memory of what his old friend had become). He would dramatically sit around and rewatch his own warning holorecordings to the Jedi over and over. Occasionally, he would have contact with his old friend, Bail Organa, because the writers saw Rogue One and remembered how fans liked to have a cameo of Jimmy Smits in the movie.
Then, a conflict arises! Something exciting enough for him to step out into the open once more, returning to his former days of a noble Jedi Knight. Ultimately something that does not matter in the grand scheme of things, but maybe it would prevent the sand people from abducting or the Empire from discovering Luke Skywalker. The young boy, played by
Jacob Tremblay, would be rescued by Obi-Wan without even knowing, possibly due to being knocked-out when the obligatory lightsaber action happens or something, only to wake up back at the farm.
Cut to a wide total shot of the moisture farm, when Luke is happily reunited with his uncle and aunt who were worried sick (more chance for some prequel love in bringing the young actors of Lars and Beru back!). And in the dark and out-of-focus foreground, a hooded figure is watching over the scenery, his gaze turned towards the sinking twin suns of Tatooine, while the force-theme kicks in mightily and transitions into the classic Star Wars credits. Wow, what a movie! Too bad we had most of this already in that one Rebels episode.