So really, this Mandalorian concept art - while it is a nice little novelty - will certainly be looked at as a possibility that some fans wish actually played out. It actually wouldn't be the craziest resurrection that Star Wars has ever pulled off - that dishonor actually belongs to Emperor Palpatine and his sudden return in Star Wars: The Rise of Skywalker. If Plo Koon had shown up in The Mandalorian season 2 finale, then it would have been a major reversal of established canon, revealing that the Jedi Master didn't actually die in the fiery crash of his ship, which was shot down during a routine patrol flight after his big victory at the Battle of Cato Neimoidia.
Like so many minor or supporting characters in Star Wars, Master Koon has gotten his own cult fan base since first appearing in the Star Wars prequels Lucasfilm made Koon a featured character of certain arcs of the Star Wars: Clone Wars animated series (including its very first arc), which has only helped to increase his amount of fans. In Star Wars canon, Plo Koon was one of the Jedi Masters that was killed by his own clone troopers during the execution of Order 66. The Mandalorian concept art by Brian Matyas. The Mandalorian concept art by Christian Alzmann. The Mandalorian concept art by Brian Matyas and Doug Chiang.
The Mandalorian concept art by Erik Tiemens.
Director went so far as to commission this fake concept art, of the character Plo Koon, to hide involvement in #TheMandalorian Season 2 finale. The Mandalorian concept art by Christian Alzmann.