It looks like the Radeon HD 3870 and 3850 are indeed the right names for the new RV670 based cards from AMD, although there’s an XT and a P which we presume means Pro on this document which doesn’t add up with what we’ve seen some sites reporting about when it comes to AMD’s new naming scheme."
Learn more at TweakTown. Keep in mind that this document might be a bit outdated as some of the pricing and performance figures aren't correct.
One of the interesting things the document lists is the R680, this card is believed to be a dual-GPU card and if the pricing info is correct it will cost a whopping $799!