And, perhaps, versions of the 4K display with and without a GPU would fit into their m.o. of making pretty high end stuff requiring low effort on the part of users.

and then if the monitors could also run iOS on their own when the computer is elsewhere ...

With as much cash as Apple has on hand it must be difficult not to just put out a single continuum Nano-Touch-iPhone-Mini-iPad-monitor-TV with OS X computers only occasionally filling a role for content creators.