Following the completion of Sword Art Online: Alicization - War of Underworld, Season 2, the official site for SAO has announced an anime adaptation for the six volume novel series by Reki Kawahara, Sword Art Online: Progressive. The new series was announced right after the final episode aired in Japan.
Yen Press, who publishes the novels, summarizes the series as follows:
There's no way to beat this game. The only difference is when and where you die…'One month has passed since Akihiko Kayaba's deadly game began, and the body count continues to rise. Two thousand players are already dead. Kirito and Asuna are two very different people, but they both desire to fight alone. Nonetheless, they find themselves drawn together to face challenges from both within and without. Given that the entire virtual world they now live in has been created as a deathtrap, the surviving players of Sword Art Online are starting to get desperate, and desperation makes them dangerous to loners like Kirito and Asuna. As it becomes clear that solitude equals suicide, will the two be able to overcome their differences to find the strength to believe in each other, and in so doing survive? Sword Art Online: Progressive is a new version of the Sword Art Online tale that starts at the beginning of Kirito and Asuna's epic adventure--on the very first level of the deadly world of Aincrad!
In addition to the announcement, Sword Art Online's official site also revealed the first visual and a promo video. Check out both below!
Sword Art Online Progressive Visual

Sword Art Online Progressive Release Date
As of yet, an official release date for Sword Art Online Progressive's anime adaptation has yet to be confirmed. When more is announced about the new series, we will update this post, so stay tuned!