after spending some time w/ the motif XS, I wouldn't be surprised to see Yamaha move in that direction w/ the next-gen arrangers. the arpeggios (which are similar to multipads) are easy to create and manipulate, and while they're not the main draw of the XS, they could be the center of a very flexible arranger. this would also allow for more modern electronic styles -- there are tons in the XS, very weak derivatives in the tyros et al.

it is time for Yamaha to retire the rather dim drum samples from the arranger line and use the motif kits....ditto some of the bread and butter sounds.
another handy XS feature is the 8 knobs and sliders on the RH side -- the next top arranger should have that, to allow for on the fly part mixing, etc.

of course, I'm also waiting for yamaha to fully implement midi and sequencing capabilities in the mm6. err, perhaps that's coming in the mm6pro???