The CRM 4 mainstream support date ends on 09/04/2013 so this might be a good time to start thinking about upgrading to CRM 2011. CRM 2011 Q2 Service update will include lots of great reasons to upgrade like cross browser support, new mobile applications, you can read more about that in this blog post
If you would like Metaphorix to help upgrading your CRM 4 to CRM 2011 please visit the Metaphorix website and contact us.
If you would like to find more information about Microsoft’s support policies there is a Lifecycle Support Policy FAQ which is interesting and below I have copied the support dates from this original page.
Products Released General Availability Date Mainstream Support End Date Extended Support End Date Service Pack Support End Date Notes CRM 1.0 1/1/2003 7/11/2006 Not Applicable CRM 1.2 10/31/2003 1/9/2007 Not Applicable Dynamics CRM 2011 5/18/2011 7/12/2016 7/13/2021 Dynamics CRM 3.0 12/1/2005 4/12/2011 4/12/2016 Dynamics CRM 4.0 2/29/2008 4/9/2013 4/10/2018