It looks like they're no longer advising members to hold off on registration as of today. Per their email to members:
Members required to register with FAA
AMA members are now required by regulation to register their aircraft with the FAA to avoid federal enforcement and potential penalties. All Radio Control modelers must register aircraft weighing greater than 0.55 pounds online no later than February 19, 2016. The registration fee is $5. However, FAA is offering free registration when registering on or beforemidnight EST on January 21. Online registration can be accomplished on the FAA webpage at, RegisterMyUAS.faa.gov . Several AMA staff members and AMA leaders have been working with legal counsel and the FAA to find a solution for our members on the registration rule. To date, FAA has agreed in principle to several proposed initiatives that will help ease this process for our members in the future. Visitmodelaircraft.org/gov to learn more.