One thing is for sure, by nvidia keeping the naming so close it'll probably make it much easier for nvidia and vendors to sell off old G80 stock until G92 cards completely supercede the old.

Unless you really know what you are looking for it would be hard to tell exactly what the differences are. If they gave the cards a new model number people would automatically select the bigger number as the latest which is usually the case for the most part.

I'm sure nvidia would love to move everything over to G92 right away as the cost should be somewhat lower for them but they still have to move old stock out first and replace it with new stock.