I don't think the limiting factor in "how much cruft should we add" is bandwidth. It's the point at which it becomes so hard to use that users leave.

Example: Buzzfeed loads in 1 second for me on my work's broadband, but it's still full of junk making it hard to use. Bandwidth-wise, it could handle more crap on the page, but in terms of usability it's at the limit.

I think you actually will get a faster and generally improved web when sites are finally able to end HTTP/1 support, because it will free up web developers from old performance hacks like asset concatenation, image sprites etc, which add a lot of friction to making websites.

All that said, this demo is bullshit for the reasons given in other comments.