ThinkSecret reports that they have heard that Xserve will take advantage of Intel's upcoming Woodcrest processor. Woodcrest is Intel's successor to the current "Xeon" server-targeted processors. There had been reports that the Woodcrest family of processors would be making it into "Macintosh workstations" as early as 3rd quarter. Indeed, Woodcrest, is expected in June of this year, with the rumor site expecting the Intel Xserve to follow in July.
Meanwhile, PowerMac revisions (Mac Pros) are expected to make the transition to the recently announced Core 2 Duo processors (codenamed Conroe). These processors are expected in July.
ThinkSecret speculates that the PowerMac revisions would come at WWDC, and indeed, MacRumors has received confirmation Intel PowerMac revisions ("Mac Pros") are to be announced at the WWDC Keynote which takes place Aug 7-11, 2006.