Blu-Ray bitrates are bloated for various reasons, like older encoders, film transfer, and a lack of anything better to do with the space. You don't need 20mbps with modern H.264 High encoders, it's just a waste. Anything past 10 is at best questionable
> By then we will at least have 4k and probably a bitrate in ~100 MBit/s
Even if 50mbps were something that we would ever need at 1080p (it's not), 4k would not justify a doubling in compressed size, there is no reason to have 100mbps compressed video.
4k is also way beyond reasonable for home display. Just 3840x2160 on a 60" display would be something like 23 arc seconds at 3 meters, you physically cannot see that.
> 60 TB is only 15 times more than we have to day in a single drive
4TB is already orders of magnitude more than most workloads will ever need. I was using video to demonstrate the absurdity of thinking typical workloads would actively use 60TB, because it's not a typical workload, it's a worst-case scenario.