While Mass Effect Legendary Edition will have over 40 other expansions and DLC to play, there are a couple of omissions within the bundle.
According to Game Informer, the Pinnacle Station DLC won’t be available due to data corruption. Pinnacle Station was originally developed by Demiurge Studios, not BioWare. The source code for the DLC has been lost, and when the studio tried to retrieve the backups, the data was almost completely unusable. In order for the Pinnacle Station DLC to be re-released, it would have to be a complete remake.
Pinnacle Station was the second DLC pack for Mass Effect and it added a training facility, along with 13 new combat scenarios.
The Legendary Edition of Mass Effect 3 also won’t have multiplayer due to the logistics required. According to an interview with The Verge, Mass Effect developer Mac Walters noted that the multiplayer has been cut in favor of improving the single-player.
Nonetheless, the remaster and its many graphical updates will be available in spring 2021 for PlayStation 4, Windows PC, and Xbox One.