A new successor to the PX-5S would be exactly what I am looking for. Considering the new PX-S line perhaps with their new (less noisy!) smart scaled hammer action, the new piano sounds, the AiR/AiX hybrid sound engine used in the PX-S series, but still with Hex layers and the extended controller functions from the PX-5S. Expression pedal port and Audio over USB would be nice, too. If it gets a touch screen like the PX-560 and the portable 3-pedal solution of the PX-S series, it would make the perfect digital piano/controller/synth workhorse.
As the PX-5S is quite old now and already hard to get in stores (is it still in production?), I hope that there will be a successor, soon.
I am currently in the situation having to decide if I buy a PX-560 NOW or wait for the PX-5S successor. The new PX-S line doesn't really appeal to me (only rudimentary MIDI controller functions, no firmware updates planned (as stated here in the forums)).