Ostensibly I do agree with you however that is the reason I phrased it "browser vendors working together" rather than "a new spec being written".

However, as you said, the chances of that happening are remote. Even putting personal agendas aside (eg Google wanting to control content via AMP), the web in it's current form is "good enough" that there's no real drive to reinvent the wheel for something with such deep market penetration already.