The dates have apparently moved to June 15th for the HD 4850 and to June 22nd for hte HD 4870 and 4870 X2 cards. There will be immediate availability on the HD 4850 while the 4870s won’t see widespread dispertion until mid-July. There a lot more “details” over at the source article:
In terms of performance, we heard some interesting claims. A 4870 should perform on par with or better than a dual-chip 3870 X2. Our sources explained to us that using a PCIe Gen1 controller 3870 X2 was a mistake, since the board was hungry for data and didn’t sync well with this interface. Don’t expect the ATI team to repeat that mistake with the 4870 X2. However, we admit that we have no idea what kind of connection two RV770 GPUs will have.
As for the NVIDIA GT200, not much more is coming out other than the name:
It is understood, GeForce GTX 200 family will be introduced early 2 models, including the GeForce GTX 260 and GeForce GTX 280, but the price, specifications have not yet announced.