Streaming services pretty much top out at 80Mbps, but more typically are around 15≃20Mbps for even 4K content, so even if they straight quadrupled the bitrate for 8K content you'd only be hitting UHD BD rates.
I don't disagree that BD will not exist for an 8K market, but that's because physical media is being killed.
This isn't even getting into the actual mastered resolution of much of this content, which you're lucky if it's even in 4K, most stuff is still mastered in 2K.