I find it a little odd how many Star Wars films we've gotten that take place before the original trilogy- the prequel trilogy, last year's Rogue One, and next year's Han Solo film. The original Star Wars doesn't feel to me like part four of an ongoing saga, even though it begins in the middle of a chase sequence. While the film establishes a larger mythology and backstory the film stands on its own. This isn't to say I don't appreciate expanding the mythology- the mythology is I love most about Star Wars, even though I have issues with how the prequels dealt with certain events. I liked that Rogue One gave a reason for the Death Star's design flaw. This was an example of ret-conning I felt actually improved the original film's story.
It was recently announced we will be getting an anthology film centred around Obi Wan Kenobi, with Oscar nominated filmmaker Stephen Daldry in talks to direct. It hasn't been revealed what will be the film's story but Lucasfilm and Disney are somewhat limited with what they can do with Obi Wan. The film can't really be an origin story since the prequel trilogy- even though its main focus was Anakin Skywalker's turn to the dark side and his transformation in to Darth Vader- was about Obi Wan's relationship with Anakin and his journey from apprentice to Jedi Master. In The Phantom Menace we're introduced to Obi Wan as a padawan learner; he meets 9 year old Anakin, loses his master Qui-Gon Jinn at the hands of Sith Lord Darth Maul and kills Maul, becoming a Jedi Knight and taking on Anakin as an apprentice. In the subsequent prequels Obi Wan becomes a Jedi Master and a general in the Clone Wars. Ultimately Obi Wan and Anakin duel, leading to Anakin becoming horrifically burned and being placed in the iconic Darth Vader suit. The prequel trilogy even ends with Obi Wan walking off in to the Tatooine desert, book-ending the trilogy, as he was in the first scene of the trilogy.
The only other way to do an Obi Wan origin is to go back pre-The Phantom Menace, with Obi Wan as a teen. For me there's not really a story there; Obi Wan's story begins with The Phantom Menace and ends with him reunited in death with his friends at the end of Return of the Jedi. The Clone Wars have already been covered pretty much by the animated series. To me- and I always presumed this would be the case- the story of the Obi Wan film would be his time on Tatooine looking over Luke Skywalker and living as a hermit. I know some people will wonder how you could make a movie out of that time period. I envision it as western/samurai film, with Obi-Wan helping people- going by the name "Ben" of course. George Lucas was heavily inspired by the films of Akira Kurosawa so I think it's appropriate to return to those works for inspiration- think Yojimbo and Sanjuro.
The film would largely be a character study, exploring the psychology of a man who's lost everything. The Republic he fought for has become an authoritarian Empire, the Clones who fought alongside him betrayed him and the other Jedi Knights, his friend and brother has become an agent of evil, for which he's partly responsible, and the Lars family- who are raising Luke- don't want a thing to do with him. It's a pretty bleak story, even though, as with the other prequel films, we know there will eventually be hope. The fact that the filmmakers behind Rogue One were allowed to kill off the entire principal cast gives me hope we could get a film that shows Obi Wan in a really dark place.
Of course, Ewan McGregor would return. McGregor has expressed interest in the past regarding a possible solo film. For people who grew up with the prequels there would be a definite nostalgic reaction to McGregor's return. And even though I have my issues with the prequels I do like McGregor's performance- particularly his final moments with Anakin. Joel Edgerton- who played Luke's Uncle Owen Lars in the prequels could also return. I'd like to see the conflict between Owen and Obi Wan. Owen would blame Obi Wan for Anakin's turn to the dark side and wouldn't want leading Luke down the path of becoming a Jedi.
I do hope we eventually move past the original trilogy's characters and events but I hold that there's real potential for a compelling and beautiful drama about Obi Wan during his life on Tatooine, a film that isn't merely another franchise movie.