What I've heard so far is something along these lines...
The R610s/R630s (I think one has a V), the low end DX10 AMD cards, are released sometime in May, likely early because they've already been bought up.
The R600 HD2900 is released in late May (23rd, 24th?), probably about a month after the "Release" date. No word on what versions will be available. What WILL be available is the 512 mb of Ram version, AKA XT.
The R600 HD2900 XTX is released later, likely June, because that's the earliest realistic time for it if it doesn't come out with the XT. No real word about this either.
The R650 chipset (HD2450, 2650, 2950?) is released, likely in late August, featuring a 65 nm core, meaning more efficient chips, but maybe more expensive due to yields.
However, my current (conspiracy) theory is that the R600 is going to be 65 nm, but ATI is keeping it all secret until the 23rd/24th, and all the R600 data we have so far is on 80nm stuff... There was so much talk about 65 nm, but now it's all gone? And why would a rare 8 pin power connector (even if it is backwards compatible) be used on a retail board?
We aren't going to be able to know anything definitive until the 23rd, so it would be best to wait patiently right now, I guess. However, we might get more hints after that on the XTX's fate, possibly through Apple or one of the other major system builders (like what happened with the 3 ghz Xeon).