Two new Dura-Aces' are coming our way from the good people at Shimano, news and images courtesy of James Huang at Cycling News.
1. Dura-Ace 7900 (prototype below), all mechanical actuation, 180g lighter, more robust shifting with increased cable and shorter shift lever throw (merely nudging the lever about 2mm or so will initiate a gear shift). Top of brake hoods feature a much flatter section for comfort. The groupset's chain will have a quick connect link, hollow pins and milled out side plates. Cassettes will be available with wider gear selection like a granny 11-28T. Nice.
2. Dura-Ace Di2, electronic shifting,100 grams lighter than the current group even with a battery pack,optional remote shift buttons for time trial and triathlons, a 'crash' position that helps shield the rear derailleur from a fall, and an auto-trimming front derailleur.
There's a nice video of the electronic shifters over at the Cycle To blog which features an input from a Skill Shimano racer. Check it out here. For more textual technical information on whats served in the 2009 electronic package, check out this discussion at Slow Twitch Forums.
Finally, to James Huang himself : Nothing shifts at the speed of light. Electrons are much slower, you'd be surprised. :)