Yes the avg speeds have increased,training has gotten better and more aero from testing in windtunnels etc.The gains from weight savings however are prob less than 1%,but the gains from better training/bike set-up are prob around 3-5% if the tdf stats are any indication.Being the right size physically is a huge component...example,pre cancer Lance was too heavy,carried too much upperbody muscle around,post cancer he was able to achieve the current typical size range and power output of a top ten elite pro stage racer.This is still gains in performance measured in seconds over MANY miles.Could Merckx compete on a 20-30yr old bike in todays peloton.....Id guess yep,on a flat stage sure,wouldnt make much difference,hilly stage...maybe,I think the results would suprise some folks.Some of the performance gains are still gonna be masked by teamwork,strategy,course,and just plain luck.