Recently I've found myself using Bluetooth speakers and more especially Bluetooth headphones to listen to a variety of media sources (particularly Audible). A relatively simple and flexible process where I can listen on a headset without inflicting the sound on others.
Achieving this for Sonos requires an expensive Amp or Connect plus a Bluetooth transmitter - crazy.
I guess this rather cumbersome setup could be avoided with the advent of Sonos headphones, but probably only at some exorbitant cost. Once upon a time, I probably would have stumped up the necessary cash, but if any headphones work only exclusively with Sonos and can't also be used as normal bt headphones, then I'll pass.