My take is that very few combined-function/swiss-army-knife devices (of ANY sort) perform as well as a separately developed dedicated device performing the same function. Sure, you can put a hammer head or saw on the end of a screwdriver but nobody would buy it, simply because it is simply not as good as it's single-function counterpart.

Arrangers (and Workstations) will continue to evolve because developers are constantly trying to create the 'perfect' arranger (or workstation). If arranger-functions were merely a 'feature' on some 'Master do-it-all keyboard', it probably wouldn't get the same level of R&D. Let's face it; Arranger players want the ultimate ARRANGER, and Workstation players want the ultimate WORKSTATION, and never the twain shall meet. Also, what Donny said; it's probably way more profitable to keep them seperate. Trust me, the corporations know what they're doing (marketing wise). JMO, though.

chas