I may be wrong! If so, please correct me.
But from what I have been able to gather, here's the deal:
The 2008 rates have not taken effect yet. BUT (and this is a big BUT) some of the 2008 rules have taken effect ONLY IF you use these new codes.
For instance, if you use one of the new room-only codes for AP in December, then you will receive a discount for some nights (like usual) AND not be given any discount for certain nights near Christmas. So you might be paying 200-something for a few nights and then have your rate change to close to 400-something for other nights of your stay.
With these new codes, they are using the new 2008 rule that your rate can change throughout your stay.