Free upgrade to CS4 from CS3.3?

Hi,

I have Adobe Creative Suite 3 Design Premium and am thinking about upgrading to CS4 when it comes out.

However I have noticed some sites advertising Free upgrade to CS4 if you purchase the upgrade to CS3.3. Is this free upgrade to CS4 valid if I upgrade from CS3 to CS3.3 now? As I read somewhere it is only valid if you are upgrading from an earlier version?

Or, if I upgraded from CS3 design premium to CS3.3 master collection, would that allow me to get the free upgrade to CS 4 Master Collection?

Thanks,
Nellie