So you're saying that although user growth is slowing, bandwidth growth is accelerating? I'd like to see your figures for that; although I'm sure that bandwidth use is growing, I doubt it's growing faster than it was 15 years ago.
We aren't streaming 4K video regularly yet, and 8K is coming up. Each time we double the dimensions, we increase the pixel data four times. We also have higher frame rates and bit depths. This is only going to stabilize after we've reached some extreme resolution with lossless encoding - we're only just now getting there with audio data.
Again, I'd like to see some data. For most uses, people are perfectly fine with relatively low-res video, so although the technical capabilities of video keep increasing, I suspect the rate of growth in actual bandwidth draw is decreasing.