No, Plo Koon does not appear in Star Wars: The Acolyte. However, a member of his species, the Kel Dor, does appear in episode 4 as part of the Jedi expedition to Khofar.

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. Like so many minor or supporting characters in Star Wars ...

In one of the Jedi group shots in the trailer, a Kel Dor can be seen standing behind members of the Jedi Order, leading some to believe none other than Plo Koon will be appearing in the show.