I doubt you're going to get much movement on the streaming bitrates.
They have to make sure they are at a rate that will work consistently across a huge array of services (including cellular and a wifi hop in home) otherwise the user gets constant buffering. On top of that, the device itself has to be capable of handling that much data. Yes, modern specs for most services and hardware are beyond those numbers nowadays but it takes a long time for hardware generations to trickle out to all users. A significant portion of the market may well still be using 802.11n wifi that was so ubiquitous for quite some time for example.
But yes. Those bitrates on video, not to mention on audio (streaming Atmos is actually ~786kbps lossy dolby digital AC-3 with some extra atmos info, vs up to ~5000kpbs for UHD disk audio) is the reason I sort of dread the death of physical media. I'm not convinced that streaming will up their game to provide anywhere near the same quality once easy access to the proper UHD is gone. That leaves services like Kaleidoscope and their insane hardware costs as the remaining avenues, but is also why I'm glad that Kaleidoscope does exist.