...Until they figure out how to attach racks (with reasonable weight capacity ratings) to carbon frames, they're not likely to become mainstream for commuter bikes....
I don't believe that's true The reason you don't see rack mounts on carbon bikes is because carbon is used for lightweight, racy bikes, where for whatever reason they don't put racks mounts (like apparently the latest Specialized Allez, an aluminum bike, doesn't have the rack mounts). I could theorize - they don't want to add any additional weight that they mounting point might take, they think if they put rack mounts on it "won't look racy enough", the lower frames wouldn't be a direct trickle-down geometry from the higher frames if they added rack mounts, etc.
Take a look at the top-end carbon Specialized Tricross -
http://www.specialized.com/us/en/bc/...1&menuItemId=0
From the description on the front page - "rack and fender fittings".
If you look at the pic you can the attachment screws for a rack.
In addition, there are several racks that are designed for bikes without rack mounts that go on the bike in positions designed to take weight for other reasons - they attach through the wheel skewer (designed to carry the weight of the rider) and either the brake bridge (designed to handle the force of stopping that same rider bombing downhill) or with a replacement seatpost clamp.
The Axiom streamliner comes to mind as the first rack I know of, I know there's a couple of Tubus racks that are designed for this as well, plus you can get adapters for their other racks.