Premieres sometime this year, likely with more information coming during AnimeJapan 2024 at the end of March. This movie takes place during the events of season 4 of the show. Synopsis of the first season from AniList:
The story takes place in the year 2138 when virtual reality gaming is booming. Yggdrasil, a popular online game is quietly shut down one day. However, the protagonist Momonga decides to not log out. Momonga is then transformed into the image of a skeleton as "the most powerful wizard." The world continues to change, with non-player characters (NPCs) beginning to feel emotion. Having no parents, friends, or place in society, this ordinary young man Momonga then strives to take over the new world the game has become.
Oh yeah, I'm also a lot less hopeful about seeing it anytime soon after release. If it's a japanese theaters only release, we'll have to wait for the bluray or the like before it can be seen by the likes of us.
There is some hope. The Rascal Does Not Dream series had a pair of movies come out last year (June and December) and the English dub for both is premiering in theaters in March 2024. So, that is only a couple months for the later of the movies. I don't think either is available to stream yet though. So...mixed bag.