Here's the official press release. If you follow the link there's a pdf with more details.
http://www.iata.org/whatwedo/ops-inf.../cabin-ok.aspx
Interestingly the official pdf gives measurements in inches slightly larger than posted by BlackBerryAddict in the original post: 22 x 14 x 8. Which converts to 55.88 x 35.56 x 20.32, in other words slightly larger when measured in inches than in cm. Since this is all still at the proposal stage, I imagine that the airlines and luggage manufacturers will resolve the ambiguity before this is all finalized. The proposal calls for a universal label on luggage that all airlines will respect, at least for dimensions. Weight allowances will still vary by airline. And airlines can still permit larger bags if they so choose.
Personally, I'm glad I didn't pull the trigger on the Rimowa Salsa Deluxe Hybrid IATA I was looking at a couple of weeks ago. If this goes through that would have been a very expensive $700 mistake. I'm putting my buying plans on hold until this is all resolved.