Barts PRO and Barts XT are Radeon HD 6850 and Radeon HD 6870, respectively, and they are supposed to launch exactly one week from now - on Friday the 22nd. But you should all know this by now.
Barts will have a go versus Geforce GTX 460 1GB and 768MB and while they should win this fight, everything seems to indicate that they will be more expensive. They are being positioned as the products that are faster than Radeon HD 5770 and 5750 but slower than Radeon HD 5870 and HD 5850.
Cayman replaces Radeon HD 5870 and HD 5850 and we are hearing that Cayman XT is going to end up branded as Radeon HD 6970 while Cayman PRO gets the AMD Radeon HD 6950 brand.
Launch date is in the last week of November, if all goes well of course.