I will post here too , because i think is more active forum:D I watched Blizzard, Making of Reaper of Souls. They did a technique like, animating displacement map for more facial expression or detail animation [ame=" https://www.youtube.com/watch?v=f7zY6MVyAFo"]Blizzcon 2013 - Diablo III Reaper of Souls Cinematic Intro…
Looks like they hooked it up to the corrective blend shape system. When the rig transitions into a blend shape it also blends into the new displacement map that goes along with it.