Yes, Mace Windu will be in the new Obi-wan spin-off. We didn’t see him die, this will give him closure and to see him meet Obi-wan in the cantina in Mos Eisley talking about Anakin/Vader/Palpatine. They also go an adventure with the two of them as he sacrifices his life for Obi-wan at the end, so he can be there for young Luke.
Get Tarantino to direct, and this’ll be my favouritist SW ever.