Suppose Zenkaiser is back for the show it would be interesting if they pulled a Solbrain and made Kaito the Ryoma of the show as a new tsuika. Or Zox or Flint is fine too.

Another Trademark that came out around the same time as the last few, potentially DonBrothers related but might not be

(Source)

Also, the "Oni Taiji" in "Don Oni Tajin" literally means "Defeat the Demon", (source) which makes me question there being a demon themed Ranger on the team like the alleged "OniSister", if the team is also destroying demons

Which tbf out of most of these rumours "OniSister" is one of the ones with the least backing behind it, so far all of the presumed real/reliable leaks only talk about Red, plus at least one claim that the black Ranger is CGI

Until we see more, I feel like any specifics about the team outside of those two claims (Red and Black) are better to take as speculation that's gotten out of hand

There more then one leak that brings up OniSister.

Almost all of that info comes from Matt Hunt (aka Dukemon on Rangerboard). He scours the Japanese message boards and relays what he's heard, sometimes from reliable sources and sometimes not. The guy is a wild prima donna who has an extremely inflated ego, but he's good at doing the legwork no one else is willing to do.

Thanks! :)

I saw Matt Hunt re-affirmirming a few rumours yesterday but still wasn't sure if he was the original source, helps a lot to know

I wonder what the Sentai Gears could become. Maybe they could be used with the Motorcycle that the Changer becomes to become a Mecha. Or maybe their powers would be based upon the monsters of the series instead of the Riders.

Also, because there are 5 New Rangers, I wonder whether they will have their own Mecha.
But, I also have some fears. Like, why would Juran be the only Kikainoid Zenkaiger to follow Zenkaizer into the new series? Considering the Magical Powers of these new Donbrothers, I'd think Magine would want to join them. Why would she not join?
Also, I think that the Red Momotaros-based Donbrothers Member would appear in the final episode and assist Zenkaizer in the final battle. That's when there would be the first introduction of this new Red "Ranger" and, possibly, the introduction of the new Robo combination of the Bike Mecha and Juran.

If this happens Imma call her super sentai Nezuko. :lolol

He's due to join in January, quite a bit before the final episode

He's an invaluable resource 90% of the time, but as the pre-release hype cycle plays out he inevitably adopts this attitude that because he aggregates all the info, his opinions and speculations hold more weight. That's when the line between the solid rumors and what he wants to happen starts to blur... so while you can generally trust what he says, you should approach the info with a hearty amount of skepticism.