I think it means a future revision of the web could explicitly identify a subset like AMP, to encourage web developers to target it without Google being involve

I think it means a future revision of the web could explicitly identify a subset like AMP, to encourage web developers to target it without Google being involved. One advantage of a setup like this would be the possibility to instruct your browser to reject any non-AMP pages (or make them click to play, or otherwise indicate them), if you were on rural internet and didn't even want to bother loading a slow page.