From Mike Neil (Virtualization GM) on the Windows Server Blog:

As the person who oversees the development plans, teams and strategy for Microsoft’s virtualization software on desktops and servers, I want to update everyone on the timing of our server virtualization offerings. I know that many of our customers and partners will hear of these changes from their usual Microsoft contacts, but I wanted to personally explain some of the reasons behind the new schedule for Windows Server virtualization (codename Viridian) and Virtual Server 2005 R2 service pack 1. But first, here’s where we stand today:

The public beta of Windows Server virtualization will ship in the second half of 2007, not in the first half as previously disclosed.

The final version of Virtual Server 2005 R2 service pack 1 now will be available in Q2, not Q1 as previously stated. In the interim, customers and partners can download a Release Candidate (RC) version later this month - this is code complete and an update to the current beta 2.

Up front, it’s important to know that Windows Server “Longhorn” remains on schedule for beta 3 will be this half and RTM in the second half. Iain McDonald and team are doing a great job delivering the next-generation Windows Server OS, which includes in-demand features like TS Gateway, Server Core, Network Access Protection, IIS 7.0, new server manager and failover clustering improvements … to name a few. All the work being done here is designed to deliver a safer, more secure infrastructure and simplify admin tasks. This work will help make customers’ experiences with Windows Server virtualization even better.

You can read the rest of the post here: http://blogs.technet.com/windowsserver/archive/2007/04/12/Viridian-and-Virtual-Server-Timing-Updates.aspx