Site Sculptor only allows you to import CSS Sculptor presets from version 3.
However, this doesn't stop you from using your presets in Site Sculptor. Regardless of what version of CSS Sculptor you own, you will probably want to create a page from your CSS Sculptor preset that you can then turn into a Dreamweaver template prior to entering Site Sculptor.
The reason for this is so that you can add additional editable regions to your template that will be turned into content areas in your CMS. If you go directly from CSS Sculptor to Site Sculptor, you are going to only have the one main content area for all the pages.