The most compelling reason to believe that the events of The Mandalorian could be low-key retconning the events of Heir to the Empire is simply that Ahsoka mentions she’s looking for Grand Admiral Thrawn. In the Disney canon timeline, the last time we saw Thrawn was in roughly 0 BBY (Before the Battle of Yavin), in the Rebels series finale, in which Ezra and Thrawn jumped into deep hyperspace on the Star Destroyer Chimaera to parts unknown. Five years later, just after the Battle of Endor, Sabine and Ahsoka reunited on Ezra’s home planet of Lothal and decided to go look for their lost Jedi friend. While it’s unclear whether Ahsoka has already found Ezra by the time Mando meets her on Corvus in “The Jedi,” she does know that Thrawn is back and operating somewhere in the galaxy.
Here’s why this matters: the year in which The Mandalorian takes place, 9 ABY (After the Battle of Yavin), is the same year in which Heir to the Empire happened in Legends. It’s hard to imagine now, but back in 1991, Heir to the Empire was the first book that truly opened up the post-Return of the Jedi era. After Zahn’s trilogy of novels, that time period started to get crowded, and by the time The New Jedi Order books were happening in the early 2000s, we knew more about the three decades after Return of the Jedi than we did about the Clone Wars.
But when the Prequel Trilogy hit theaters, Lucasfilm began to invert that trend. Suddenly we knew way more about the pre-A New Hope era than we’d ever known before. And once the new Disney canon took hold in 2014, those three decades after ROTJ that had previously been filled in by the Expanded Universe were suddenly swept away, leaving, more or less, a series of question marks between Return of the Jedi and The Force Awakens. Sure, recent games, comics, and Star Wars Resistance fill in the gaps a little bit. But other than stand-out examples like sections of the book Last Shot, or the novel Bloodline, those lost years previously occupied by the bulk of the EU haven’t been “replaced” entirely in the new canon. We assume Mara Jade never existed, and all that stuff with Luke, Han, and Leia fighting a clone version of the Emperor in Dark Empire never happened. But are we sure?
The potential re-introduction of Thrawn in 9 ABY makes a revised version of the Heir to the Empire storyline and some of the EU books that followed possible. In fact, it might all still happen in a modified form under Disney canon. It would be like the Star Wars version of Star Trek’s “Kelvin Universe,” the timeline in which the reboot films exist. What would this look like? Maybe Thrawn is back, and Mara Jade is back, too, but this time around, there’s no Joruus C’baoth, and nobody is using the quaint designation of “Dark Jedi” and they’re just calling people “Sith.”
A rebooted Heir to the Empire wouldn’t even need to be explicitly remade or rewritten to still work in the new canon. Even if Disney doesn’t reboot this story, you could also just treat it as head-canon and it would still fit in nicely with the rest of the canon timeline. Here’s how: If stories set in The Mandalorian timeline continue to avoid Luke, Leia, and Han and the bulk of the New Republic, it’s easy to imagine everything that happened in the old books still happening up until the events of Vector Prime and the ensuing Yuuzhan Vong invasion that made up the bulk of The New Jedi Order book series.