I dont believe they sell the 8120 in retail stores do they? As of a month or two ago it was an online only item (ATT that is), and was only available from the business premiere site when i got mine a while back. I think they stock the 8110 because it is a more affordable phone for the general consumer (but in my opinion 8120 is tops because you can add a bluetooth puck for next to nothing, and then you have it all in one little phone).
I know there are a couple phones in the works, the Bold being the first blackberry 3g to hit ATT. I would project this phone being somewhere in the ballpark of $400 with a contract, and in all honesty, i would not be surprised if it soon after blows the iPhone sales out of the water
There are 2 more new phone models which i believe are essentially 2G, if you google upcoming blackberry phones you can find a wealth of information.