Well, it bet its to compensate for the lack in of team interaction in the Taisen movie since its a Kamen Rider War with minimal Sentai allowed. I mean, even looking at the release date, its pretty darn close after the movie comes out.

I appreciate that Toei is doing more cinematic universe stuff with the setup they have already.

Behind-the-scenes filming shot!

I'm pretty sure that's for Kamen Rider Taisen.

Taisen's out in just over a month; they should have finished filming by now...

It has to be from Taisen. Those are the soldiers from the Badan Empire. Which was ZX's big bad evil organization. And they're the main villains of Hesei/Showa Taisen.

I was wondering who those grunts were, heh.

Further details from TV-Asahi:

*The one-hour special will replace the normal SuperHeroTime block that weekend.
*The teamup will also include special cameo appearances from Kamen Rider 1, 2 and V3! (probably in-suit only, no mention of actors so far).

We've got a teaser.
https://www.youtube.com/watch?v=UxQtlVj5ewQ

And people said that image was from the Kamen Rider movie...
Also, obligatory "hey maybe Kouta's ToQ Rokugo cuz der both orange lol"

Cool