Ugh. Again with these iPad 3 rumors. Since when did people forget that apple reserves new numbers for completely redesigned products? They didn't throw more memory in the iPhone 3G and call it the iPhone 4, did they? They called it the 3GS. New numbers are reserved for completely redesigned products. They're not going to throw a retina display in the iPad and call it the iPad 3.
Heres how I see it going down: they announce potentially 12 models (I'd say 8 is more likely, as they'll probably just offer 32gb and 64gb models and drop the 16gb). Coming out soon would be the non-retina display model (wifi and 3G models), then later this year, for a heftier price tag (because you're crazy if you think they'll offer a retina display for the same or lower price point than the current iPads), you'll have the option to get the models with retina displays and maybe built in sd card slots. Both will still be considered iPad 2, or simply iPad (2nd gen).
This strategy would make sense as it would let the casual audience that doesn't care about retina, and would rather save some cash, order right away, and it would still keep apple in the tablet race this year because everyone would know a retina display model is in fact coming near the end of the year. Apple wouldn't lose sales, and it keeps them competitive. Makes sense.