From what I understand, I don't think the BLM will have the annual passes for sale at the pay station that weekend. You will need to buy them from a retailer ahead of time (if available). If they are not available yet at that time, you will have to buy a week pass and that $$ will count towards your annual pass when you buy it. The BLM is still working out the details. I am sure will will be notified by the TRT or BLM once everything is in place.
The latest will always be posted on the homepage and here on the forum so don't worry- you will the 1st to know whats up.