doing some quick excel analysis of the wiki data, the 2:00:00 barrier will be broken sometime around 2040. This is using linear regression of the WRs from 1967 on and a logarithmic regression (chosen for best R^2=.967, I am no statistician) of all of the data gets almost exactly the same result. Personally, I would think that the barrier will be hit some years after that, maybe late 2050s.