As one of the few people using an Arranger for live work I'm always conscience of how much is the Arranger doing and how much am I doing, so for me I've got enough in my BK9 to keep going in the future. And properly editied it sounds pretty good and not 60's home organ fake. I've seen acts with no instruments, just singing over tracks and I don't want to fall into that.
So the point is the balance between some arranger "help" and having it take over.
Home players love all the fancy stuff. And how many pro or home players know how to fully use all the features that are already there?
I've said this a few times before but manufactures for the most part really drop the ball when it comes to educating people on how to fully use their wonderful new machines.
So adding more will cost more and further confuse most buyers. Look at some of the audiences in the in store demos for these keyboards. Amazed by the demostrator but can the go home and emulate the fancy things they just witnessed?
I think there's enough hardware out there now and the future is VSTs.