We recently re-opened the upgrade window to allow registered users of 2006 and earlier versions of Delphi, C++Builder and Borland Developer Studio to upgrade to the XE versions. If you have one of those older versions, you only have until end-of-day this coming Tuesday May 31, 2011 to buy at the upgrade price. After that you'll have to again pay the full new user price if you want to move to XE or a future version.
Remember you can also combine this eligibility with the Get RAD Studio at the Delphi/C++Builder price offer and pay just the Delphi or C++Builder upgrade price and get full RAD Studio XE with Delphi, C++Builder, Delphi Prism and RadPHP.
Here's the link with all your choices for How to Buy.