The Old World was the setting for the entire Warhammer fantasy line-up and myriad spin-off games all they way from the game's introduction in 1983 to the apocalyptic "End Times" multimedia event of 2015, when culminated in the entire planet literally exploding. Subsequently a new setting coalesced from the ashes, paving the way for the Warhammer: Age of Sigmar product line.
Age of Sigmar did extremely well on release, although it's more recent performance has been variable. This may be down to the age of the line (coming up on five years) and Games Workshop's launch of a new edition of their traditionally better-selling Warhammer 40,000 science fantasy game in the meantime.
The timing of the original event was considered a bit odd, given a major new video game set in the Old Game was just about to be launched. Total War: Warhammer was released by Creative Assembly in 2015 and sold gangbusters, raising interest for the fantasy setting. Total War: Warhammer II followed in 2017 and also did extremely well, with a third game due for release in the next couple of years. It is probable that the success of the video games has played a role in the decision to resurrect the old setting.
Fine details about the decision have yet to be released. It has not yet been confirmed if the Age of Sigmar product line will be ending, with the Old World being recreated by the End Times event being undone, or if this will be a historical line set earlier in the timeline with the Age of Sigmar and Old World product lines coexisting.
Whatever the case, we have a while to get used to the idea: Warhammer: The Old World will not be launching until late 2022 or early 2023.
