The reason in the e-mail is that:
By this fall, however, upcoming platform technologies including Windows Server 2008, SQL Server codenamed “Katmai,” Visual Studio codenamed “Orcas” and Silverlight will already be in developers’ hands and approaching launch, which is where we’ll focus our developer engagement in the near term.
It's not clear exactly what this means--they don't want to have a conference to pimp stuff we can actually play with? Nagel got pissed at them for stealing his art for their logo? They can't afford PDC because they spent so much on aQuantive?
Well, it's disappointing. PDC is a great conference, filled with intelligent people. It's rewarding as a partner to go see what's new and what people are doing (both from Microsoft and from other partners). I was looking forward to it.
Microsoft has more new development tools available now than ever before in their history. .NET 3.0 is still new, and the virtues of WPF, WCF, WF and InfoCardSpace (or whatever they ended up calling it) can still be sung to the partners. And certainly Orcas and Silverlight deserve close looks and more education.
I think it's a shame--and I'll be sure to let them know that at the Worldwide Partner Conference in July.