ATI's R520 will be called Radeon X1800 and three different flavors will be available in October: Raedon X1800XT, Radeon X1800PRO and Radeon X1800XL.
Someone at ATI said it's so good that it deserves twice as big a number than 900 and ended up with X1800 as a product name for this new Radeon based on R520 marchitecture which features support for Shader Model 3.0 and some other interesting video features
The RV530 core for the mainstream market will be called Radeon X1600. This card will have to battle the NVIDIA GeForce 6800 and will be priced at $199.
Then there's also the entry-level RV515 which will be named Radeon X1300. This one will retail for around $99.