Although analysts argue that Microsoft should rather wait in releasing Windows 7's first Service pack, Microsoft should deliver it by the end of the year - the last quarter of 2010.
When Microsoft first released Vista in 2007, company executives argued that a service pack wouldn't be necessary because Windows Update could deliver fixes as they became available. Microsoft later backed away from that position. It hasn't made the same argument about Windows 7.
Microsoft will issue the first service pack for Windows 7 later this year