sub-2h estimator wrote:
2:06:05 Ronaldo da Costa Brazil September 20, 1998
2:04:55 Paul Tergat Kenya September 28, 2003
2:03:59 Haile Gebrselassie Ethiopia September 28, 2008
2:02:57 Dennis Kimetto Kenya September 28, 2014
(All Berlin Marathon)
It's been roughly 1 minute down each 5 years. So sub-2h around 2030 would be a fair estimate. But it all depends on doping, some freakish talent coming along, and the course/organization/race.
That only works to a point then you reach human limit. For example track times steadily improved but for the most part have plateaued. The marathon was behind the curve because it took longer to gain the same attention from elites as the track. We're very close to the plateau. We'll see the record broker a few more times but not significant chunks coming off.
Unless you get a weird day on a loop course where winds change and are super helpful. Or "scientific" jumps.