I think the additional audio payload is irrelevant - just watch the extras disappear if the studios think they can make more money out of the release (or releases). The latter will be the sole driver IMHO. Also, we are on the verge of 4k BR so it's difficult to predict the future. My money is on object-based audio becoming the norm.

Main system - Sources (Kodi-HTPC, Vero 4k, FireTV, Sat) into Trinnov Altitude 32 (8-16) (+Roon), Trinnov Amplitude 8 amp & Vivid Audio (Giya G3, V1.5) and REL Stentor III speakers. Others: F80 + Raspberry Pi and other Pi systems.