What basis do you figure this? Being the main villain don't mean sh*t to Bandai.
In all likelihood, Phoenix would probably get made first.

The thing is, Medusa, at least for now, seems hardly a big villain. In my opinion, Phoenix is more memorable as a character, plus has a cooler design.

Wait...there's more than Flame, Water, Hurricane, and Land?

I'm already figuring that the'll be a "Man behind the man" sort of thing, where she'll either die or a stronger Phantom will appear and take the role as primary antagonist.

I'm guessing it on the basis that Medusa seems to be the primary villain in the early part of the show, like Scorpion was in Fourze. And Scorpion was made first in that case. But I'm not trying to argue the point. Just a stab in the dark.

The way they've depicted them, Phoenix is kind of a toady. Has he even fought anyone yet?

No, but we're only on the 4th episode so I'm sure we'll see him fight eventually

Is it just me or Medusa in phantom form kinda looks like Insarn From Gokaiger?

Nope, Medusa reminds me of her also. I think it's the lower face/lips.

The first two episodes didn't appeal to me very much but episodes 3 and 4 were pretty good. I think I might be into this show now. Cat Sith ruled.

Right? I think its the same suit but with some changes. I also thought Hellhound kinda looked like Rio from Gekiranger with the faceplate.