A very interesting post, however I doubt if anything will change on this front, as the days of the Hardware Arranger/Workstation are seriously limited. (In 5 years or so I would say that they will just be a distant memory)
The reason for this is, yes you’ve guessed it the computer, so in the future you will purchase your keyboards as laid out below.
All manufactures will produce keyboards with different layouts of Buttons and Screens, with all variations of keyboard size/feel, you the customer will then purchase the one you feel happy with, all the keyboards will have one thing in common, a standard computer interface that will work with any software arranger/workstation, but they will look and operate just like the old Hardware Arranger/Workstations, (As they are just keyboards they will be stocked in both Workstation and Arranger shops) you will then choose what software instrument(s) you require, such as Tyros, Motif, G70, SD1, Triton etc, then you or the shop owner will load the instrument(s) in, and away you go. (If you want more then one software instrument, then you will just purchase it and load it in)
The future is closer than you think.
Just thought I would give you something else to ponder over.

Bill