Rumors from Yobuko. Long time since I saw him post. Probably a fake Yobuko, but whatever. I can actually see this happen.
Date fell for a trap that Maki had set up.
Gotou finds out about what really happened and transforms into Birth.
OOO goes ShaUTa liquid mode, takes out the bullet in Date's head.
Date officially retires as Birth. Hands over the belt to Gotou and tells Gotou to fight with Eiji and Ankh as a combo.
Gotou refuses the belt and hands it back saying Date is the only one who should be Birth. Until Date fully recovers, Gotou will fight alone.
Maki's experiments failed, he's completely swallowed by darkness and Giru is formed. Eiji is also affected by this.
Ankh is absorbed by Lost Ankh. To save Ankh, the lost 10th Core Medal is needed.
Mezool gets closer to Kougami. Uva is revived, he falls in love with Satonaka.
Kougami knew Maki's sister when he was younger.
Movie and TV series is connected. Hina looks exactly the same as a princess, she is kidnapped by ninjas. Ankh and Gotou are mistaken as a samurai and Nezumi Kozo, respectively.
Fouze and Metamoru shows up in the summer movie. (Metamorufouze → Metamorphose)
Metamoru may or may not be a second Rider, Yobuko didn't say.
http://en.wikipedia.org/wiki/Nezumi_Koz%C5%8D in case you haven't heard of him.