Otoya's actor recently mentioned Masao in his blog, alongside Otoya, asking something about going as them... Even remembering Masao is strange, so I suppose he could be returning as him.
However, Masao used the standard Kiva suit... would they really feature 3 different Kivas in the same series? Even if that picture is old, I think Dark Kiva makes more sense.
Besides, Otoya only died early as Dark Kiva thanks to Wataru messing up the timeline. Originally, he used it enough times to at least use the weapons of the arm monsters (he knew that he could call them and knew how to operate them perfectly when he possessed Wataru's body in the present, even though he didn't even remember his own death).