That OOO movie has nothing to do with Den-O shit.

Anyways.. KAmen Rioder Phose rumors

Kamen Rider Fouze uses items called "Rider Switch"
Fouze has five basic forms.

The setting is in a high school and revolves around the school's Occult Club.
The Occult Club consists of three members and their club advisor.
The story is about the Occult Club investigating the urban legend about something called "Kamen Rider", and collecting past Rider Switches.
In the start, Fouze already has his five Fouze Switches and four OOO Switches.
When he has 5 Rider Switches, he can metamorphose into that Rider's Mode. (Note, the poster was using the word metamorphose. If this is true, Fouze is probably romanized as Phose)
He can access past Rider's Modes. He doesn't exactly become the Rider like Decade. Easiest way to describe this is Den-O Plat Form being equipped with different parts. Basically Fouze has a base form and he's equipped with the past Riders armors.

There are 3 different type of Switches. First one is Rider Switch, which changes the body of Fouze. The second one is Arms Switch, this one is for various weapons and such.
The last one is Vehicle Switch, it's used for the bike and other support mechs.

The enemy organization is aiming after the Switches too.

It doesn't seem like past actors and Riders will show up, but Fouze will debut in OOO's Summer Movie.