The code for SQL Server 2008 (Katmai) has made it to the RTM phase, according to the closing keynote at TechEd South Africa. This essentially locks up development for this version. Downloads should be available soon to MSDN subscribers and trial availability relatively soon for non-MSDN subscribers. Physical media and availability in retail outlets will be a bit longer (date unknown).

Press release here: http://www.microsoft.com/presspass/press/2008/aug08/08-06SQLServer2008PR.mspx