Looks like Shimano's new Dura Ace carbon wheels were on display this past weekend (on top of a Team Sky support car.) These look like 60mm rims to me, but they could be 78mm depending on the perspective.
Interestingly, it appears these wheels are set up for 10 speed, so they probably didn't go on the bikes that have been testing the new 11 speed Dura Ace 9000.
Photos after the jump:
16 spokes on the front wheel:
20 spokes on the rear wheel:
Straight pull hubs and bladed spokes.
Interesting design on the non drive side flange, and a 10 speed cassette?