Similar to what The New York Times did for the 100m dash in 2012, The Wall Street Journal has developed a great graphic to show just how much faster the top speed skaters have gotten over the years. The still above is part of an animation pitting every male 500m gold medalist against each other; the 2002 winner (Casey FitzRandolph) would have beaten the 1924 winner (Charles Jewtraw) by almost 10 seconds.
Top speeds increased steadily until 2002, but the trend seems to have leveled off a bit. Also, as the Journal points out, the very fastest finishes since 1998 have all occurred on high-altitude tracks, so it's very unlikely that anyone will be breaking any records at Sochi (where the course is 89 feet above sea level). It will probably still look really fast though.