Dengeki Online has released the cover art for the final novel in the Alicization arc of Sword Art Online.  The previous two covers in the series focused on characters other than Kirito.

For Volume 16, Asuna was the main focus with her new form shown.

For Volume 17, Sinon and Leafa were featured in their new goddess forms.

Now for Volume 18, Kirito returns as the center in this cover. Kirito is shown wearing his Black Swordsman outfit from the Aincrad arc. Asuna wears the outfit that debuted in Volume 16 of Sword Art Online and is depicted alongside Kirito. You can check out the new cover below (unfortunately no larger size available right now).

The Alicization arc of Sword Art Online is the longest arc in the entire series. It has 9 volumes released right now with one more set to release in August. This is more than the Aincrad, Fairy Dance and Phantom Bullet arcs combined.  Those arcs had 6 volumes altogether.

Sword Art Online Volume 18 Alicization Lasting is set to release on August 10, 2016.

SOURCES: 1, 2