The Sword Art Online - Extra Edition anime special, recapping the Aincrad and Fairy Dance arcs and including new footage, is now scheduled to run on December 31st. Looks like the original content is basically going to be a swimsuit episode.
The latest on the anime is that it's going to run for two hours with the light novel author Reki Kawahara contributing to the script and illustrator abec contributing designs.
In its original story, the characters accept an ALO underwater quest when they learn of Yui's wish to see a whale. Discovering that Suguha/Leafa can't swim, Asuna takes the girls to a real world pool for training. Meanwhile, Kirito is having mysterious meetings.