Borland upgrades for most products are allowed from any previous version (Delphi 1 is no longer allowed though AFAIK).
That was always one of their strong points (and maybe a potential weakness from a sales perspective).
I think they now abandoned it for JBuilder though, which may point to a less bright future (but then, the entire license model and version spectrum for JBuilder was changed which makes it far harder to determine which previous version would be equal to what current version).