IMHO arrangers will morph into workstations and be more software based. It just makes sense to have a system that can be customizd and upgraded as needed by the user. Why companies don't do this more is strange. They could charge for the software updates so as not to loose income from selling new keyboards.
It seems there are so many keyboardists out there using laptops for sounds and effects live that the soft synth market will only grow.
Bill, very few musicians I know have the patience to learn and use soft synths and arranger software, taking advantage of vst's.