E-ink should already be able to produce 12.1" panels as stated on their site (there is even a sort of prototype e-Textbook by SurfaceInk with this screen).
About the Skiff Reader, yes, that would be perfect... If we were talking about UFOs instead of eReaders or Tablet I would have said there's a sort of coverup for >9.7" readers
Dozens of prototypes all discontinued, vanished or vapourwared