Well, I like that a lot more than I hoped I would. The future is looking grim for my finances.

...and there went my hopes for a cooler-sounding driver. I want to find whoever is in charge of these increasingly-shrill Driver sounds and shake that person silly. When Fourze and Wizard seem tame by comparison... (I know some people are into it, and I'm happy for them. But UGH.)

Get ready for Heisei Generations: It's Not Actually Heisei Anymore But We Couldn't Think Of Another Name next year, I guess. Final kind of wasted some of the returning actors, so I'm not super pumped about this one. Guess it would be nice if they could get Philip back?

Lot of actors from previous KR are busy right now though. Don't know if we can expect an appearance.

Ghost, Ex-Aid, Decade, Den-O are busy.
I want to bet 555 (always around with anniversary thing) and Blade (appeared in GoRider 1 year ago as well as decade years ago so why not) can appear

I can see Drive's actor coming back, after not being able to join Heisei Gens Final.

I was going the actors from Heisei phase 1 to make a comeback appearance in the movie.

Kuuga-Decade

Joe Odagiri has said he'd 'come back for a Kuuga reunion movie, but not for anything else', so he's not coming back, certainly.

Toshiki Kasshu, Takamasa Suga, Kento Handa, and Takayuki Tsubaki would all come back, schedules allowing.

Shigeki Hosokawa is involved in a court case, so he's not likely, either.

Hiro Mizushima's expressed interest in returning, despite never having done so before.

Takeru Satou's agency will likely not let him return at this point, with how famous he is, although the Taros will likely make an appearance.

Koji Seto...has never returned, so who knows.

Masahiro Inoue and Renn Kiriyama would likely come back, schedules allowing - although Masaki Suda likely wouldn't.

Shu Watanabe, Sota Fukushi, Shunya Shiraishi, Gaku Sano, Ryouma Takeuchi, and Shun Nishime would also all likely return, if able.

I'm not sure about Hiroki Iijima.

And Atsuhiro Inukai is likely contracted for it, like Koji Seto was for Decade.

As great as Godai was, I'd like to see characters like Ichijo or Enokida reappear.

Wonder if Zi-O causes a Flashpoint, Ichigo would be the Jay Garrick mentor to him. Reasoning with him on the decisions he made with messing time.

Both are busy with a musical named Shirotora (with Ryuga from GARO as well), so not sure if they are available if the musical is on tour.

Decade's Masahiro Inoue is busy with his own GARO Spin-off, starting October on TV (and unlike Kamen Rider, GARO asks a lot from their protag on a physical level for fighting scenes as they rarely have body doubles for their impressive choreographies).
So don't know if he can be available enough to shoot a KR movie and a GARO show at the same time.
I would expect a short appearance in the show, because anniversary + the upgrade thing, but I would not expect him to that present.