they can start by taking the governor off airPlay -- it currently converts every thing to ALAC: 16/44.1 before sending it to the selected endpoint. even roon, using an airPlay endpoint, downsamples hi-res files to 16/44.1
Airplay 2 is in out of testing right now. It was announced at the last WDC.
best i can tell, airPlay 2 is for iOS devices and allows them to stream to multiple sources. haven't seen anything indicating they are changing the aipPlay protocol where streams are transcoded with ALAC at 16/44.1... just haven't seen anything, so could be wrong about this.
Now all they need is high resolution content to stream to their devices. Regardless of what people's opinions are of both Apple and MQA. Having MQA or high resolution content on Apple Music would help high quality be more accessible to many more people.