According to this page,
http://support.microsoft.com/lifecycle/?p1=16497, support for MOSS 2007 SP 2 will end on January 8, 2013.
MOSS Service Pack 3 does not have an announced end date for support, but Microsoft has announced that its not going to be putting out any further Service Pack level updates for MOSS 2007, so I would
not expect that product's support window would extend more than a year or two past the date for SP2. The second page I linked to may be updated once they announce an actual date. You can also check here for lifecycle information for all Microsoft Server Products:
http://support.microsoft.com/gp/lifeSelectServ
John
MCITP and MCTS: SharePoint, Virtualization, Project Server 2007
My books on Amazon: The SharePoint 2010 Disaster Recovery Guide and
The SharePoint 2007 Disaster Recovery Guide.
My blog: My Central Admin.