My Take On The Ending (Spoilers)
Just a theory, but I like it. The robot at the end looks over at Frank briefly. I'm assuming that after Frank was put into the nursing home, Hunter would have sold Robot to someone (after all, it must have been very expensive). What IF, that robot at the end was actually Frank's robot with his new owner...and the look the robot gave Frank was a a brief flicker of recognition? Maybe the reformat had left a tiny residual memory of Frank in Robot's brain? Not enough to remember much, but enough to just make him glance at Frank.
A sort of Robot Alzheimers maybe.