Can't see how anyone would think the Tyros4 would be "massively upgraded".

It's just another iteration of the Tyros.

If there would be an arranger with massive upgrades, it wouldn't be called a Tyros...it would be an entirely new model, with a new name.

On the other hand, Yamaha's way of upgrading each new Tyros model has proved very successful.

I'd be very surprised to see Korg come up with a massively upgraded PA*XPro...in fact, I'd be surprised if there will be another one at all.

Ian