This picture shows on the case that it is a Privia which is their digital Piano line. I doubt that they would release a powerful synth and call it a Privia. That would cause confusion.
My guess is they will release a new Privia Piano which would not need a large LCD like we see in this picture, and another synth.
My guess is that it will be based on Phase Distortion (Casio's take on FM) and they will call it a CZ like the many CZ Phase Distortion synths in the 1980s.
If they did that they could easily also include the same VA monosynth that is in the XW-P1 and XW-G1 or even make that a Poly.
Then they would have two very powerful synth engines in one keyboard, making it the most powerful synth they have ever made