On October 11th 2012 Exchange 2013 and Lync 2013 reached the RTM state.
I have been part of the RDP and TAP program on Exchange 2013 since February and it has been a very exciting journey where I have been able to earn and see Exchange 2013 evolve to what you all will see in a very short time, when it’s reach GA.
As a start Exchange 2013 will only be supported in new installations, which means that we will have to wait until 2013 to begin upgrade existing Exchange 2007/2010 installations.
There is now direct upgrade path from Exchange 2003, so you will need to upgrade to Exchange 2010 first, and then deploy Exchange 2013.
Read more from the Exchange Team blog: http://blogs.technet.com/b/exchange/archive/2012/10/11/the-new-exchange-reaches-rtm.aspx
And don’t forget to read the Lync Team blog: http://blogs.technet.com/b/lync/archive/2012/10/11/lync-2013-is-finished.aspx