Whether Decker will have evil human cast depends on how they will do Fake Dyna and final boss, I guess.
Fake Dyna does have human form aside of its true monster form, meanwhile the final boss doesn't despite hailed as Ultraman replacement by Guts scientist who created it.
Yeah, not only its just for one episode but also its like telling "Perhaps" to Zero fanbase that always wanted Mamoru Miyano doing its human disguise.