Well, it is expected that March would be the release time frame for XP 64 and PDC 2005 isn't until September 2005, thats a big gap in between March and September to promote the product (5-6 months). Visual Studio 2005 would be expected 2 months later after
XP 64 which would give Microsoft some time to show off some of the new 64 bit capabilities.That would leave little for the company to talk about the product at PDC '05 and most of interest on Longhorn.
Pocket XP, its not impossible for Microsoft to surprise us and release the beta 1 for Longhorn September 2005 to coincide with PDC 2005. This would further push beta 2 out to February or March 2006 or earlier if they have progress which can result in a short
Sticking to my original prediction (June 2005), I suspect that a beta 2 would come in January 2006 and could possibly push the final release out to November 2006 if you take into account release candidates.