It's possible that Wizards of the Coast is working on a new book that will add revamped playable monster races to Dungeons & Dragons, as many of them were scrapped or replaced last year. There's a D&D book called Volo's Guide to Monsters, which has stats for a number of monsters, allowing them to be turned into playable races that can be used in campaigns.
There are races in Volo's Guide to Monsters that are no longer part of D&D rules. In 2020, Wizards of the Coast overhauled the race rules in D&D. The playable monster races in Volo's Guide to Monsters were singled out as being retconned, as they had stat penalties. The intention going forward is to make all of the races viable, and giving some of them penalties makes them less attractive in the eyes of players. This is especially true in the current edition of D&D, where none of the races in the Player's Handbook have penalties. Wizards of the Coast released errata for Volo's Guide to Monsters, which removed the stat penalties.
A new version of the race rules was introduced in Tasha's Cauldron of Everything, and they make it easy for players to change existing races, or rework them into something brand new. The information present in Volo's Guide to Monsters is now considered outdated and Wizards of the Coast might be gearing up for something that can replace it in print form.
Dungeons & Dragons' Missing Hobgoblins & Kobolds
Unearthed Arcana recently added fairies, hobgoblins, owlfolk, and rabbitfolk to D&D. There was another article that revamped the dragonborn, as well as adding gem dragonborn and a new version of the kobold that can choose its draconic ancestry. Unearthed Arcana articles usually offer hints as to what books are coming in the future, and these two were no exception, as the fairies and rabbitfolk will be appearing in The Wild Beyond the Witchlight, the owlfolk will be in Strixhaven: A Curriculum of Chaos, and the gem dragonborn will be in Fizban's Treasury of Dragons. This leaves the hobgoblin and the kobold unaccounted for.
It was during the press event for Fizban's Treasury of Dragons that representatives from Wizards of the Coast mentioned that not all material in an Unearthed Arcana article is connected, and some of it is being saved for future books. It's unlikely that they have been scrapped, as Wizards of the Coast has been upfront about the Mages of Strixhaven subclasses being cut from Strixhaven: A Curriculum of Chaos. The fact that these are playable versions of popular monsters could mean that a new monster guide is on the way and that it will officially supplant Volo's Guide to Monsters.
If such a book is in development, then it likely won't be released until 2022, as the 2021 schedule for Dungeons & Dragons is packed. It's possible that it will be sandwiched between the upcoming classic campaigns that are set to launch next year. The new book could not only revamp the rules for playing as these monsters but change the lore around them, to put them on equal footing with the humanoid races in the Player's Handbook, in terms of their culture and society, so that they're not just fodder for adventurers.