At some point, all aero bikes (both road and TT) will have truly integrated brakes like the Speed Concept and BMC TM01/TMR01. I love my S5 to death, and I have a suspicion that it's a faster frame than my buddy's TMR01, but with standard brakes and exposed brake cable, it just doesn't have the sex appeal of the TMR01.
What I predict will happen (and it will likely debut on the successor to the P5), is that Cervelo and Magura will work together to create a hydraulic brake "module" that will fit in a fork (and frame) cutout that will completely hide both brakes within the lines of the frame. This module will basically bolt-in to the frame and fork cutouts, and brake adjustment will somehow be accomplished by either screws that move the position of the module within the cutout or there is a sub-assembly within the module that moves to allow brake adjustment. With hydraulics, you are basically going to never need to adjust the brakes (unless you change wheels), but nonetheless, the adjusting screws for this could be placed in such a way that ProTour mechanics could continue to hang out of team car windows to adjust brakes on the fly. And the rear brake could be kept at its traditional seatstay location to allow for on-the-bike adjustment, since it would be integrated into the frame and you wouldn't need to "hide" it down by the BB.
I know what the numbers say, but Cervelo needs to find a way to integrate brakes into their frames. Sure they could come up with something mechanical like their competitors, but if they do that, they will only be playing catch-up. Integrated hydraulic brakes would absolutely see P5 owners lining up to buy the P6 and would do the same for S5 owners moving to the S6. But the P6 will be easier because you can use Magura's existing brake levers - getting this done on the road will be more difficult.
Amateur recreational hobbyist cyclist
https://www.strava.com/athletes/337152 https://vimeo.com/user11846099
