There's two possiblities, either they only come out with the iPad 3. And that's it. It'll have retina, more RAM, and it'll have either a quad-core A9 or dual-core A16. It may be over $500 for the lowest end model though.
The other possibility is that the new iPad will be basically an iPad2 with a higher clocked processor but it'll still have the retina display and probably more RAM. If this happens, then they'll probably keep the current iPad2 around as the lower tier model, but I don't see them selling it anywhere near as low as Kindle Fire territory so I'm not sure how lucrative it would be to keep this tier.
The problem with the first option is that it'll just be expensive. The problem with the second option is that they might not wait another whole year before updating the iPad with a new processor. Plus it would throw out the chronological naming scheme since they might just call it the iPad2 HD/+/Retina or whatever.