I'd be very surprised if Kushida sang the OP theme; they haven't gone for an older performer for a long time. (Remember when the trend was to at least have an older performer like Kushida or Isao Sasaki or Ichirou Mizuki for the ED theme? They even stopped doing that!)
Maybe Kushida's doing the voice of the toys, even though that would be repetitive after OOO..?
And while I'm not the biggest Kushida fan, it would be cool of him to have a new OP, and to be chosen for the anniversary. If it turns out to be him, I guess this show did want to have a couple of homages to Sunvulcan. I guess you can thank Asao Kobayashi for being a Creepy Cosby Bastard why it's not a panther to go along with the eagle and shark.