as others have said, better representation of modern music styles -- reggaeton, house, etc.,

integrate an arpeggiator with the arranger functions -- for generating multi-pad-type backing sequences on the fly.

finally, and mainly: upgrade the keybed of the middle/upper range (S710, S910): it's almost criminal to offer all this sound-shaping and arranging power and then yoke it to a basic, ie, not terribly musical, keybed. even the Korg PA500 has better feeling keys than the 910.