While I am a fan of the concept of increased braking performance, two issues I believe will greatly slow the adoption of disc brakes use in road and time trial racing are increased weight and increased drag.
“Discs will add somewhere between 250 and 750 grams, depending on the component choices made.”
“Do discs harm aerodynamics? Most likely, yes. Bike brand Culprit did some wind tunnel testing comparing its Legend frame with and without discs, and found that the discs increased drag. The difference was dependent on yaw angle, and ranged from 1-10 watts, with the largest difference at high wind angles.”
“This is, of course, a massive argument against the adoption of discs for racing. Ten watts is similar to the gains found from a set of aerodynamic wheels — it’s certainly not insignificant”