The following contains spoilers for Obi-Wan Kenobi Season 1, Episode 6, "Part VI," now streaming on Disney+.
Obi-Wan Kenobi was a difficult series to judge. It had some incredibly awesome moments -- all the lightsaber combat was phenomenal and the tomb in Fortress Inquisitorius was perfect for Darth Vader's Inquisitors. However, the Disney+ series was also plagued by pacing issues, forgone conclusions and having to finagle in established Star Wars canon. The finale was a microcosm of the show's highs and lows.
Plot holes were abundant in "Part VI." There was no reason for the Empire to abandon the hunt for Roken and the Rebels. Vader easily could have followed Obi-Wan alone on his shuttle. Reva letting Luke live felt contrived and Obi-Wan should have killed Vader. But despite all that, the episode managed to end the series on an incredibly high and hopeful note. That ending might also have set up a surprising villain for a potential Season 2.
Obi-Wan Kenobi was designed as a limited series -- but neither Lucasfilm president Kathleen Kennedy nor director Deborah Chow have completely ruled out a follow-up. When questioned on the possibilities of a sequel, Chow said "It would only be if there was a real reason for another one." The return of Mace Windu could be that reason that makes Season 2 worth producing,
When the finale ended, everything seemed perfect. Luke Skywalker was safe and Reva had turned back to the light side. Meanwhile, Obi-Wan defeated Vader and embraced the hopefulness that defined him in A New Hope. As he was riding off into the sunset, Qui-Gon Jinn's Force ghost appeared, indicating that Obi-Wan would soon begin additional training with his former Jedi master. With all of that positivity, only something massive could test Obi-Wan's newfound attitude enough to warrant a second season.
Windu was presumed dead after Revenge of the Sith, but fans (and Samuel L. Jackson) have made repeated pleas for the Shatterpoint-using Jedi to return. So far, Disney and Lucasfilm have done nothing but tread water on the subject and there really hasn't been a good opportunity for him to resurface. His appearing in Obi-Wan Kenobi would be the monumental return he deserves -- especially if he were a villain.
Windu could have been hunting Anakin Skywalker ever since Revenge of the Sith and find Obi-Wan on Tatooine. They could tentatively team up to fight the Empire... but there would be a problem. Windu would find out that Obi-Wan was protecting Anakin's son Luke. Wanting revenge and determined to avoid the same mistake the Jedi Order made in training Anakin, Windu would go after Luke. That would force Obi-Wan to fight a former friend to protect both Luke and the galaxy.
While this would be an amazing Season 2 plot, it would admittedly be difficult to see Windu as a villain. Along with Yoda, he was a bulwark for the light side during the whole prequel trilogy. Seeing him turn to darkness would be uncomfortable to watch and many Star Wars fans might be upset by it. However, it's the best opportunity for his return. If Disney and Lucasfilm have any interest in bringing Mace Windu back, they need to make him part of Obi-Wan Kenobi Season 2.
All six episodes of Obi-Wan Kenobi are now streaming on Disney+.