There will be a SP3 for SQL 2005.

Jens Suessmeyer posted on the MSDN Forums today the link to her blog with information about SQL 2005 SP3. There will in fact be a SP3 coming after the release of 2008 to the public later this year. This is good news for the SQL community where there have often been questions about which Cumulative Update or hotfix should be applied, and what the support level of those would be.

http://blogs.technet.com/dataplatforminsider/archive/2008/04/15/sql-server-2005-sp3-coming-soon.aspx