How many years after the silver Turing Test is passed will an AGI system be developed?

Given the public disagreement of expert opinion on AI timelines, seen for example here, there is a need to establish a credible track-record of accurate forecasting in the lead-up to the development of AGI.

Oren Etzioni, head of the Allen AI institute, recently published an article on identifying 'canaries' which will presage the imminent development of AGI. He proposes that limited versions of the Turing Test could present a natural canary.