Well at this point
most of us can only
guess what will happen, and I'd be hard pressed to say the MOTL PSR would go to 76 keys, when they don't feel a 76 TOTL model is feasible, and they already have a piano based arranger in the DGX line.
Far more likely they'll cut a few more holes in the DGX case and add more accompaniment variations and extra intro/ending buttons.

Why go to the bother to s-t-r-e-t-c-h, the PSR case, when there is one already available with 88/76 notes in the DGX line...they even have pitch bend wheels.
For argument's sake, I guess they could stencil PSR over the DGX letters, and there you'd have your 88/76 PSR.

;D
That's my take on it, for what it's worth.
Ian
[This message has been edited by ianmcnll (edited 05-19-2009).]