The Hour Record

How much has velodrome technology increased speeds? have the boards themselves got better?

There's probably room for improvement in the actual choice of board material, pine planking is chosen for a mix of reasons and I don't think minimising rolling resistance has ever been one of them. There are aspects of track shape which influence speed, notably the distribution between curves and straights, with long curves favouring pursuit (but making match sprinting pretty dull, as it becomes almost impossible to win from the back in a reasonably close match). There is always a problem with the transition from straight to curve, and a separate but related problem of having the black line lie in a single horizontal plane. The 1996 Atlanta track was designed to be 'flat' using a computational model which wouldn't have been available for such a trivial task until the 1980s, but I don't think it's an approach which has been widely adopted. It seems that there is scope to model the interaction between a bicycle and a track surface to minimise resistance at a given speed. The UCI has minimum and maximum permitted track lengths for competition, which precludes making a tiny 'wall-of-death' track for record breaking :-)