As far as I know
Kuuga doesn't exactly hate Kamen Rider or Tokusatsu. He just doesn't care. I guess he can come back if Kuuga's producer is involved. If any character from Kuuga is to show up in these movies, I think it would be Kaoru Ichijou.
Agito has reprised his role at least three times and Gills expressed interest in coming back two years ago or so. Dunno about G3 or G4, but Jun Kaname (G3-X) has recently accidently hit a little girl while driving in his car, so I guess he's out of children-related films for some time. It's not helping, that he apologised via his agency and not in person.
Ryuki and Odin have reprised their roles twice (in games), with Suga (Ryuki) also coming back as Ryuga. Knight, Zolda and Ohja were all interested in coming back. Also, Zolda, Raia, Imperer and Femme all did @Tokusatsuhero twitter, cheering up kids as characters from Ryuki during Japan Earthquake 2011. Ryohei Odai is also voice for Zolda in Ganbaride now and seeing how Kurata first got in Ganbaride and now coming back for a movie, I think it's safe to assure we'll see him sooner or later.
555 main trio all made appearances in Toku recently. Dunno about Psyga, but Kiba/Orga's still hanging around on 555 reunions.
All 7 Blade guys were back at some point. Duh.
Hibiki also did @Tokusatsuhero twitter. Most of other Riders from TV-Series came back in Decade (as did Kirameki, though as AU Agito).
Kabuto is kinda big now. I guess that's why he didn't come back for anything. He did @Tokusatsuhero twitter, though. Gatack and Hoppers has reprised their roles multiple times and Drake isn't exactly stranger to the Toku, too. Caucasus was back for the recent BW game. Dunno about Sasword, Hercus or Ketaros.
Den-O is fond of his role (he did @Tokusatsuhero twitter), but his agency won't let him do it again. I honestly don't get how these agencies work. If you don't want him to be associated with the children show, why let him do it in the first place? Do you believe once he's big, everyone would just forget about his Den-O role? That's just stupid. Everyone else from Den-O is pretty much avaliable.
Kiva, I guess has same issues as Den-O or Kabuto. Everyone else were back at some point (well, except for Arc, but who cares about him?).
Everyone from Decade and onward are pretty much avaliable, except for Philip and (thankfully) Fourze. It's probably their agencies, too.