Infinity Ward pushed out a massive patch for Modern Warfare and Warzone, with no actual information regarding "new" content. The official patch notes mention a new playlist update, new blueprints and gulag loadouts, weapon changes and adjustments, along with a ton of fixes. However, those updates couldn't possibly add up to a 28 GB patch.
The same patch though also allowed players to access the previously sealed bunkers in Verdansk, if they were able to find a key card. Within the bunkers, players have discovered nuclear warheads, unknown caches and weapons, and more. With the third season coming to an end in a couple of weeks, we are already seeing Infinity Ward set the stage for Season 4. More importantly though, it seems they are taking on a Cold War theme, and possibly looking to add a map changing event as Fortnite has.
Verdansk is now reportedly set to change in the coming weeks, with new locations that will make Warzone more "chaotic". The revamped map is said to be connected to the bunkers, which in turn is also connected to the Black Ops installment, titled Cold War. Infinity Ward will be paving the way to Black Ops by revamping the Warzone map for the fourth season.
Activision recently stated that Warzone will continue to be supported for future Call of Duty installments. The publisher wants to “bring players together seamlessly in one unified online multiplayer playground” instead of releasing multiple multiplayer games altogether. With that being said, it's a clear indicator that Warzone will be changed accordingly to the next game in the series, and proves the point of the new map being a Cold War theme.
Data miners were able to find a number of new weapons that have been most likely set aside for season 4 of Modern Warfare and Warzone. That being said, data-mined files are not always guaranteed, and many changes can occur.