Face tracking software plus directional microphones means you don't need actors to wear any extra gear. There are methods of using a microphone array so that individual voices can be picked out of a crowd, even in a stadium full of people. There's also face-recognition software that can find faces in images in real-time. Put them together and point them at a stage full of actors and what do you have? A system that allows actors to work on stage without lapel or head microphones, requires no batteries or transmitters, and gives crystal-clear sound reception regardless of house speakers, audience noise or other actors.
It also makes it possible for the sound desk to use an idiot-proof visual interface, showing actors' faces and their volume levels either on a grid or in real spatial orientation. Someone should make that. Every time I've worked on stage with microphones, there have been some kinds of problems, either with hiding the transmitters under costumes, batteries going flat or cords interfering with physical motions. This kind of system would eliminate all of that in one go.
Mokalus of Borg
PS - Of course, other things could (and would) go wrong.
PPS - Starting with any time the actors turn away from the cameras.