Hello,
It should be possible to import a site created in older version to Kentico
CMS 6.0. When importing packages from an older version of Kentico
CMS to a newer one, structure of the package is always converted to the newer format automatically.
Please pay special attention when importing Form user control, Inline control and Web part objects from older packages. If possible, avoid overwriting your current objects of these types with objects from older packages, as it may cause incompatibility problems.
Best regards,
Michal Legen