The final BD on sale June 26 will include a new short story with the title: The Day After. Kawahara says it will be about Kirito, Asuna and "one more character".
At the last character song album all the girls sing together and Kirito sings with them
The title of the song is "Sing All Overtures" and here is a sample:
http://www.swordart-online.net/package/index09.html
http://www.animenewsnetwork.com/news...xt-short-story
http://sgcafe.com/2013/05/sword-art-...a-final-bddvd/