Just as it does with Windows, Microsoft typically offers its Office customers an upgrade guarantee program, allowing them to buy the current version of a product with a free or discounted upgrade to the next one being part of the package.
One of my contacts said the Office 2013 upgrade guarantee will begin in about a month's time -- specifically on October 19. If this is correct, users purchasing Office 2010 between that date and the end of the covered period (which my same contact said is April 30, 2013) will get some kind of guaranteed upgrade to Office 2013 once it is generally available.
Microsoft officials have not shared public guidance as to Office 2013's planned release-to-manufacturing (RTM) or general availability dates. My sources have heard that the RTM target is November 2012, with general availability slated for February 2013. (Those with TechNet/MSDN and volume-licensing agreements would likely get the final bits shortly after they RTM.)
Read more at source:
Microsoft preps its Office 2013 upgrade program | Microsoft - CNET News