[Sunred]

Zenkai does primarily mean to go all out and knowing that a machine theme is gonna be involved maybe we will get a gimmick-heavy year for 2021. We could get keys or batteries again maybe or if they wanna try something new, key cards that activate the gimmicks when in very close proximity to the toys. Of course, we will have to wait at least 4 more months roughly but with a name like Zenkaiger I am expecting Toei and Bandai to go big.
As for the rangers I see a few possibilities, they could be either:
a. They are all humans who just happen to use machine-themed powers
b. They are all cyborgs or robots
c. Red ranger is either the sole human or cyborg/robot of the team