DAAMIT will show the R600XT 512 MB GDDR3 card next week, but only under NDA. This card is ready since before Cebit, but the driver was not.
With a new driver called 8.361 the card has a fighting chance. April 23rd and 24th are reserved for NDA presentations of the Radeon HD 2000 generation, but this won't be the time for the official introduction.
The official introduction is scheduled for the middle of May and we have heard a few times that the guys are talking about the 14th of May as the official launch day.
R600XTX is delayed until June if not later, as this GDDR4 card would be expensive and it doesn’t bring that much of a performance increase. The BOM (Build of Material) cost is much higher than that of the GDDR3 R600XT card.