Spoilers ahead: If you have not yet seen The Mandalorian season 2 finale, continue reading this article at your own risk.
The existence of a Boba Fett series has been heavily rumoured right from the very beginning of The Mandalorian. In season two we were finally reintroduced to Fett, played by Temuera Morrison as he helped Din Djarin (Pedro Pascal) on his path the bring Grogu to the Jedi. After playing his part, Fett splits from the group along with his companion Fennec Shand (Ming-Na Wen) and jumps into hyperspace.
After the credits have rolled on the episode we are treated to a post-credits scene which reveals the title card for The Book of Boba Fett and a date of December 2021. A Boba Fett spinoff was not part of the Disney Investor's Day announcements, but this isn't the first time that Disney have kept something quiet to avoid spoiling their plans.
So what is The Book of Boba Fett?
Theory 1: It's just the title of The Mandalorian season 3
Given that Djarin has now fulfilled his obligation to bring Grogu to the Jedi (I did warn you there would be spoilers), series 3 will need a new focus.
There are unresolved threads that the series needs to address, such as Mando's possession of the Darksaber which Bo-Katan Kryze (Katee Sackhoff) needs to legitimise her claim to Mandalore. Reclaiming Mandalore itself would seem to be an obvious choice for a series titled The Mandalorian.
There had also been rumours that Fett would take over as the lead character of the show, but with the aforementioned unresolved issues and Pascal coming out recently to address this year's earlier rumours of tension with the production team, this seems even more unlikely.
Theory 2: It's a brand new Disney+ show
To me, this theory holds the most weight. With Fett's return to Tatooine at the end of the episode, he clearly has some old scores to settle. The given release date of December 2021 does match up with the third season of The Mandalorian, suggesting that the series' may retain some kind of link. With Mando returning to Disney+ in late December, it seems that The Book of Boba Fett may be a short limited series that leads up to its return.
Jon Favreau, one of the forces behind the highly successful Marvel Cinematic Universe, previously said that The Mandalorian would follow a Game of Thrones style route with characters and story lines, sending them off on their own arcs, and this ties in with this month's announcements of new shows for Ahsoka and Rangers of the New Republic, and also fits neatly with Fett getting his own spin-off too.
Ahsoka and Rangers are already said to be linked and crossover with each other, and The Book of Boba Fett would mean that there are now four interconnected shows that share a common cast and space in the timeline. It seems that when Favreau mentioned Game of Thrones he was attempting to throw us off the scent that really Disney are creating an MCU-style ecosystem of shows within the Star Wars universe.