The big news is here :)

Exchange Server 2013 Service Pack 1 Coming in Early 2014

Few notable improvements are:

 

  • Windows Server 2012 R2 Support
  • S/MIME support for OWA Support for S/MIME
  • Edge Transport Server Role

 

For further details , check the Exchange team blog @ http://blogs.technet.com/b/exchange/archive/2013/11/20/exchange-server-2013-service-pack-1-coming-in-early-2014.aspx