http://www.korg.com/us/news/2018/042703/

Doesn't seem to be much there besides the VOX V860 volume pedal compatibility, and the Curve presets for the volume/expression pedal, basically the same as the releases for the PA300/PA600/PA900 from a few weeks ago (http://www.korg.com/us/news/2018/0410/).

Hoping that big update for the PA4X still comes soon...