SQL Server team has been very busy building SQL Server 2008 R2, meanwhile the Release Services team has posted expected timeframes for upcoming service packs for SQL Server 2005 and SQL Server 2008:
SQL Server 2008 SP2. Microsoft targets release in Q3/CY2010.
SQL Server 2005 SP4. You overwhelmingly requested another servicing release for SQL Server 2005. Given your feedback Microsoft targets now such release in Q4/CY2010. Based on current support volume as well as the fact that SQL Server 2005 will enter into extended support on 4/13/2011 we anticipate this to be the last Service Pack release for this SQL Server version. Extended support for SQL Server 2005 will be available through 4/12/2016. Please see http://support.microsoft.com/lifecycle/ for specifics. As always, the SQL Server team will carefully monitor customer feedback as well as support volume to re-assess our decisions based on your needs.