I've been reading ITU docs for about ten years now. They can be convoluted, as befits a United Nations organziation such as they are.
IMO,
Cube is most correct.
The ITU says that sometime in the first half of 2012, they hope to come up with a definition for "4G".
However, they're not really concerned with what's called 3G or 4G. (Especially since, for political reasons, sometimes organizations will arbitrarily hide behind either other term. E.g. WiMAX supporters have sometimes categorized it as 3G simply so that countries will allow them to use 3G reserved airspace.)
The ITU defines their own categories as IMT-2000, IMT-2000 Enhanced, and IMT-Advanced. They usually consider any 3G method that's been boosted (like UMTS-3G with HSPA) as IMT-2000 Enhanced.
Also, the idea that something has to START at 100Mbps to be IMT-Advanced, is not correct. The ITU charts IMT-Advanced for mobile as starting around 20Mbs and going up. The oft-quoted 100Mbps is the upper end that the technology should support, or at least be aimed for with R&D, but even that has not been codified yet.
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In short, as most people suspect, 4G right now is simply a marketing term, and the ITU recognized that it is being used as such.