The much anticipated Exchange 2010 SP3 has been released along with SP2 RU6 and 2007 SP3 RU10. There are links below to the actual KB articles below. Note the excerpt below about coexistence between Exchange 2010 SP2 and Exchange 2013.

NOTE: Exchange 2010 SP3 allows Exchange 2010 servers to coexist with Exchange 2013 CU1, which is also scheduled to be released in Q1 2013. Customers can test and validate this update in a representative lab environment prior to rolling out in their production environments as an important coexistence preparatory step before introducing Exchange Server 2013 CU1.

Exchange 2010 SP3

Features: Coexistence with Exchange 2013, Support for Server 2012, and IE10

Documentation: http://support.microsoft.com/kb/2808208

Download: http://www.microsoft.com/en-us/download/details.aspx?id=36768

 

Exchange 2010 SP2 RU6

Documentation: http://support.microsoft.com/kb/2746164

Download: http://www.microsoft.com/en-us/download/details.aspx?id=36716

 

Exchange 2007 SP3 RU10

Documentation: http://support.microsoft.com/kb/2788321

Download: http://www.microsoft.com/en-us/download/details.aspx?id=36708