Not sure if its the same in pathfinder, but back in 3.5, creatures always reverted to their "true from" upon death. Unconsciousness as well, just checked polymorph subschool in PH2.
Note: possible exception - Baleful polymorph, under extream and improbable circumstances, could be permanent. It would, there for, not revert in form. Of course, you could argue that permanent and instantaneous are different durations mechanically, even though they are the same in effect, so only the instantaneous would not revert, but permanent still could. I point out Permanency as a reference regarding dispelling, which i would consider the closest similar rule to the situation, and let you make your own decision.
I could not find anything regarding these rules in the Pathfinder version of the Polymorph sub school. I would go with the 3.5 rules unless you can find something current regarding this
