The Hollywood Reporter says
Temuera Morrison will appear in the second season of the Disney+ streaming series,
The Mandalorian. His role in unknown at this point. Some sources say Morrison, who played Jango Fett and some of his clones in the prequels. could be playing Boba Fett, a character said to be hinted at in a couple of episodes. There's also speculation he could be playing a clone again, as one of the secondary characters appeared to have a patch on his sleeve connected to the facility on Kamino. We may have to wait until October to know for sure, when the new season begins.
My guess is he will be taking on the role of Captain Rex. With word of Ahsoka Tano being played by Rosario Dawson in the second season as well, Rex who has had a close connection with her makes the most sense. Rex was brought into modern cannon with Return of the Jedi so we know he is likely still alive during this time. Rex like all the clones are just a copy of Jango Fett, so a real life Rex would need to be played by Temuera Morrison.