Toei is releasing Spin-off one after the other. A week after the end of Gaim Gaiden: Kamen Rider Gridon Vs Kamen Rider Bravo, we are going to get "Kamen Rider Saber Spin-off: Kenshi Retsuden" which will focus on the Five Swordsman → Kamen Rider Blades, Kamen Rider Espada, Kamen Rider Buster, Kamen Rider Kenzan & Kamen Rider Slash.
(Trailer is present in the above video at the end)
An Interview with Mei Sudo's actress Asuka Kawazu had revealed that she will appear in Kamen Rider Blades and Kamen Rider Espada's part. For Kamen Rider Blades part it will focus on where he was born, how he was raised, what is the reason he is fighting for. Touma is confirmed not to appear in any of the parts. But it's pretty suspicious why Mei is going to appear in Blades and Espada's parts even though she is not related to their past and mostly related to Touma.
As per the schedule there will be only 4 episodes focusing on individual five riders and each episode will be titled as "an episode of Kamen Rider...". So one of the Rider will have the fused with another Rider.
In the interview, they have only mentioned about Blades, Espada and Slash's episode. Trailer had featured Buster with Slash and Kenzan was seen fighting Desast. So Kamen Rider Kenzan will get his own episode. But when it comes Buster, his episode will be combined with that of Slash.