I think we should bear in mind that the PA800 isn't a replacement for the PA1X but rather the PA80.

I think the PA80 only had one assignable slider and the new PA800 now has two so is therefore an improvement on it's predecessor.

The PA1X is still the flagship Korg arranger and when it's replacement is released it may well have all of the new benefits of the PA800 and eight assignable sliders too.