Most people assume that Boba Fett died in the Sarlacc Pit when Han Solo pushed him in there in Return of the Jedi, but what The Mandalorian Season 2 maybe presupposes is.... yes, that's actually true. Boba Fett is dead.
An interesting new casting rumor for The Mandalorian Season 2 claims Timothy Olyphant will "wear Boba Fett's armor," even though Temuera Morrison is also supposedly in the series, and apparently (maybe) playing Boba Fett.
So, how many Boba Fetts do we have here? How can you wear Boba Fett's armor and not be Boba Fett? How can you be on the council and not be a master?! It's not fair!
Actually, if we think practically for a second here, the idea that somebody is wearing Boba Fett's armor could point to the obvious fact that Boba Fett really is dead. Here's why.
Speculative spoilers for The Mandalorian Season 2 ahead.
Why Boba Fett might be alive in The Mandalorian Season 2
The idea that Boba Fett survived falling into the Sarlacc Pit in Return of the Jedi mostly originates in the 1991-1992 comic book miniseries Dark Empire. In that series, set 6 years after Return of the Jedi, Fett revealed to Han and Leia that he was back from the dead and totally out to collect a bounty on Leia. From that point, the old "Expanded Universe" of Star Wars books and comics just kind of kept going with the notion that Boba Fett was alive.
Keep in mind, George Lucas approved all these books and comics, and there's reason to believe Lucas almost added a scene in the Return of the Jedi special edition where Boba Fett would have been alive. Lucas also, at least at one point, suggested Boba Fett is alive in the new canon.
So if you want to know why people think Boba Fett survived, the answer is mostly George Lucas, but also cool comic books.
But for real, is Boba Fett alive in The Mandalorian Season 2?
In the current new "real" canon, after Return of the Jedi, the answer is no. There's been nothing in the post-2014 rebooted Star Wars book, comic, cartoon, or film canon that even suggests Boba Fett is alive after that movie. Until The Mandalorian, or another canon source reveals otherwise, Fett is dead.
How can Boba Fett be dead, but also be in The Mandalorian Season 2?
Over on Slash Film (where this casting news originated), there's a theory that if Timothy Olyphant is playing someone wearing Boba Fett's armor, that means he's playing a guy named Cobb Vanth. In the Chuck Wendig books, Cobb Vanth is a dude who scavenges together some Mandalorian armor that seems very likely to have been obtained by Jawas who hit up the Sarlacc Pit.
Slashfilm's logic goes like this: If Temuera Morrison is playing Boba Fett, then Olyphant must be playing someone who stole Boba Fett's armor. They're not wrong that Cobb Vanth fits that description, but if someone has Boba Fett's armor, then it could just mean that Boba Fett didn't get it back because he's still dead. Olyphant could be playing Cobb Vanth — or any other joker in Star Wars — but as long as he's wearing Boba Fett's armor, then Boba Fett is still dead until we're told otherwise.
Could Boba Fett still be in The Mandalorian Season 2 anyway just with new armor?
Sure. That's fine. But, that only hypothetically happens if Temuera Morrison is actually playing Boba Fett.
Because the entire Clone Army looks like Temuera Morrison, he could very well be playing Captain Rex (a former Clone commander who became a Rebel) or any other surviving Jango Fett clone. He could also be playing an ancestor of Jango Fett in a flashback. Or Boba Fett in a flashback.
Just because Temuera Morrison is in The Mandalorian doesn't mean he's playing Boba Fett. Or if he is, we don't know for sure that he's playing an alive Boba Fett contemporaneous with Mando and Baby Yoda. Mandalorian Season 1 certainly used a lot of flashbacks to tell the story of Din Djarin when he was a little kid. So there's no reason to think we couldn't get Boba Fett flashbacks this time out.
From a certain point of view, the fact that Olyphant would be wearing Boba Fett's armor only seems to reinforce the idea that Temuera Morrison isn't playing Boba Fett, and that Boba Fett is really dead. Either way, if one episode of The Mandalorian Season 2 is just a lengthy discussion between various helmeted badasses talking about why everyone is wearing certain pieces of armor, we're totally fine with that.
The Mandalorian Season 2 hits Disney+ sometime in late 2020.