It's not really oversize spindles that everyone is working on, it's oversize bottom brackets. Cannondale is on the right track with this idea, and the rest of the industry will be following shortly.
Shimano Octalink and Isis both cram an oversize spindle into a standard BB shell, and the result has been a decrease in bearing life relative to a square taper bb - bigger bb in same shell = smaller bearings = decrease in life span.
The reason you aren't seeing Isis bbs from Phil Wood or Chris King is they know you can't stuff a quality bearing set inside a standard shell if you are using a hollow oversize spindle.
The "oversize" standards that are beginning to emerge are all an attempt to solve this problem by increasing ID of the BB, and are largely being fueled by the Isis BB manufacturers, who are getting pretty sick and tired of explaining why their bb's don't last more than a season.
When these BB's start appearing, they for sure will not be limited to roadbikes - they're going to be on everything. In 5 years, everybody will have some kind of oversize bb on their bike, bet on it.
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