Last week, Microsoft released the Community Technology Preview (CTP) version of SQL Server 2008 SP2. You can upgrade any version of SQL Server 2008, from Workgroup to Enterprise version.
SQL Server 2008 SP2 CTP includes lot of new features, like support of all data-tier application (DAC); report builder 3.0, ATOM feed render,
You can download SQL Server 2008 Service Pack 2 CTP from here.