Curious, has there been more development and studies on aerodynamics of disc vs rim where the disc bikes are optimized for them?
It’s tough to decipher because there hasn’t been much independent analysis. But Cervelo says, for example, that their new S5 is more aero than the prior S5’s. So disc brakes weren’t so much of an impediment that they can’t at least match the aero-ness of prior bikes. I think others, like Specialized and Trek, have said the same. But these are often with “tricks” like flush-mounted thru-axle systems without built-in levers.
My suspicion is that disc brakes will always be a marginal detriment in both weight and aero in terms of absolute design space. But only very marginal.