Some Physicists (H. K. Eriksen, J. R. Kristiansen, O. Langangen, I. K. Wehus) have calculated how fast Usain Bolt would run, if he did not start to celebrate before the finishing line. The paper is available at http://arxiv.org/abs/0809.0209
By digitising video footage and then fitting a smoothed spline they are able to give estimates of Bolts time assuming, either that his speed at the end would match Thompson, or that he kept his acceleration 0.5 m/s2 after 8 seconds. In these two cases, we find that the new world record would have been 9.61 +/- 0.04 and 9.55 +/- 0.04 seconds, respectively, where the uncertainties denote 95% statistical errors.
Usain Bolt breaking 100m record in Beijing
His coaches prediction of 9.52 is within the error bars, but could be called optimistic based on size of the 95% confidence limits. World record times would be valid with more favorable conditions so it is likely that Bolt can run 100 m faster than 9.5 seconds in the future.