The second promotional video for Sword Art Online (SAO): Alicization released, showing off new footage along with the new opening and ending songs by LiSa and Eir Aoi. The 2nd promotional video showed some old footage from the first, but it revealed a ton of new footage that we haven’t seen yet and further explaining the rules of this new world.
It is also revealed that SAO: Alicization will air in four cours. It’s currently unknown if the anime will run for four consecutive cours or will be broken up between different airing seasons or different years. It’s also unknown how many episodes these cours will be. SAO: Alicization could be run from Fall 2018 to Winter 2019 taking a break from Spring 2019 and finishing up in Summer & Fall of 2019, making the newest SAO season around 50 episodes.
Series writer Kawahara Reki also revealed on Twitter that SAO: Alicization will start broadcast on October 6th, 2018 with an hour-long episode :
"The one-hour first episode special will premiere at 24:00 on October 6 (Sat)! Since it is four-cour, it is going to be a very long series, but I would be glad if you can enjoy it till the end! I will also do my best...!"