The newly opened Warzone bunkers (opens in new tab) are reportedly part of a grander plan to reveal the next mainline Call of Duty, which is rumored to be another Black Ops entry subtitled Cold War (opens in new tab).
Reputable leakers and independent sources have supported the rumors of Cold War, and as VGC reports, its impending release will supposedly shape the Warzone map through a Fortnite-style battle royale meta-narrative. Unnamed sources told VGC that the nuclear warhead found in Warzone's secret 11th bunker will be used to effectively reset the battle royale's map, not unlike the time rifts and volcanoes used for Fortnite's map overhauls. This fits with a comment from Infinity Ward narrative director Taylor Kurosaki regarding the macro story of Warzone (opens in new tab) (although he did, notably, dismiss the Fortnite comparison in a later interview).
These map changes remain unconfirmed, but this reveal strategy would also fit with Activision and Infinity Ward's plan to maintain Warzone as a constant (opens in new tab) for the Call of Duty franchise. Kurosaki previously described Warzone as "the throughline that connects all of the different various sub-franchises of Call of Duty," so while Warzone was built and released alongside the latest Modern Warfare, it's entirely possible it will be used to help launch a new Black Ops.
Likewise, it would make sense for the release of a new Black Ops to drive changes to the Warzone map, not unlike the influence of the Special Operations in Modern Warfare, which may yet lead to a new map in Urikstan (opens in new tab). And with Warzone slated for PS5 (opens in new tab) and Xbox Series X (opens in new tab), Activision would logically want to lean on it for Black Ops rather than iterate on the Blackout battle royale in Black Ops 4.
Several Black Ops entries rank among the best Call of Duty games (opens in new tab), so we're game for another one.