I am curious whether the date will be kept. The CU1 for Exchange 2013 has been announced for 02.04.2013. The CU1 enables the coexistence of Exchange 2007/2010 servers with Exchange 2013. The CU1 will then also support the migration from Exchange 2007/2010 to Exchange 2013.
http://blogs.technet.com/b/exchange/archive/2013/03/25/exchange-2013-rtm-cu1-status.aspx
Time to prepare the test environments 
Dann hab ich ja am Dienstag gleich auf Exchange 2013 umstellen.