I don't beleive that horses are getting that much faster, it would take many years(instead of the last 5 yr) to really improve the breed.
I do think that tracks today are much harder than in the past, thus, horses running faster.
Also, shoeing plays a big role in that horses are able to give max. effort that their bodies are not able to withstand over time and thus they break down. Look at the #'s for the BC turf races, year after year need about the same # to win. This is because you can't manipulate a turf course as much as you can with a dirt course. Any thoughts.