The official website for AnimeJapan 2021 states the event will still be held from March 27 to 30.
After previously announcing that the event would go ahead at Tokyo Big Sight in March, the organizing committee behind AnimeJapan revealed today that the 2021 event would be online only.
He also runs a YouTube channel about Japan stuff called TheDoctorDazza, tweets at @DoctorDazza, and posts photos of his travels on Instagram.