Greenspan has been so highly regarded in so many circles that he will likely leave a very impactful legacy. I believe that many a future Fed Chairman will take a cue from Greenspan's M.O. and hence the Greenspan effect will likely be felt for many years to come. The market will likely assume that the new Chairman will maintain the methodology employed by Greenspan and will likely not panic until shown otherwise by screw-ups on the part of the new Chairman.