Nah, it's in the realm of impossibility. Oda was watching over the production of Strong World, so he wouldn't have allowed for Shiki get defeated there by Pre-TS Luffy and then have Post-TS Luffy team up with Law in order to take down Shiki again. Even though the movie is non-canon, Oda still wouldn't have allowed for Shiki to be the villain if Shiki really was Kaido.
