The slow adoption of [hydraulic] disc brakes on road bikes is coming and the Colnago C59 disc version launch, was a clear and loud signal. I have my reservations to them being on road-racing-specific bikes. There are a number of issues that haven’t been fully addressed for me. I really see they’re place in cyclo-cross racing where the technical specifics lean nicely to disc brakes.
My main worry is that it’s a consumer demand gone too far – I will readily admit I like the looks of the disc brake bike, it cleans away some aesthetic clutter and replaces it somewhere less obtrusive – but, has little to do with real added performance value over the specific problems it brings, therefor negates the whole thing. Time will tell where this will go, if the known issues are addressed it will no doubt become a more standard option. BikeRumour has a nice piece on the issues and it can be read here.