Toei did some filming of Let’s Go Kamen Rider today in Japan. They had actually been looking for extras since early January, they were mainly looking for families and younger people and one of these extras has posted some information he heard over the set. 

40 years ago, the Riders were defeated by Shocker. Shocker has been ruling over the world since then.
OOO, New Den-O and Ankh has been crucified and are standing before the population of Japan.

The three of them are about to be publicly executed, Ankh goes to possess Momotaros. The one ordering the execution is General Shadow and he calls for Rider #1 and #2 to do the execution. It seems like the two of them are working for Shocker now.
When it’s time for execution  the Boy Rider Squad shows up and gives the Riders their belts. It’s then revealed that they had broken the brainwashing a long time ago and instead of executing them, they release them.
Together the 5 of them fight against Shocker.

Currently, it’s not confirmed whether this information is true or not, however considering the photographies have been mentioned by several posters of 2ch it’s very likely that this is true.