Good question. :) I don't want to look up exact ages for everyone, but I would guess that this graph would look more like a teepee, since Yudkowsky, Musk, Bostrom, etc. would be shifted to the right somewhat but are still younger than the long-time software veterans.
The subset that you can get birth years off the first page of a google search of their name (n=9), has a pretty clear correlation with younger people believing in harder takeoff. (I'll update if I get time to dig out other's birth years.)
http://reducing-suffering.org/predictions-agi-takeoff-speed-vs-years-worked-commercial-software/