Call of Duty 2021 has appeared on Battle.net under the codename "Slipstream" and has been updated near daily since being added to the service.
This was spotted by BlizzTrack developer Helba, who tracks library and store updates to Battle.net and has spotted Slipstream being updated over the past few days.
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#CallofDuty what is this logo that was slated right along side Call of Duty 2021 assets in https://t.co/DZWiyUuqNz pic.twitter.com/cjxK7eOMC2
— Helba (@Helba_The_AI) June 30, 2021
Beyond some CDN manifests, Helba has also spotted several developer builds and even a logo for the game. The Slipstream logo is very reminiscent of games like Medal of Honour and seems to confirm that the game is returning to a World War 2 timeline.
It's made clear the Slipstream is indeed this year's Call of Duty title as it is referred to as "COD2021" in its code, as well as being referred to as "Fore". There aren't many games on Battle.net that are unidentified, so even without those clues, it was pretty clear to Helba that this was Call of Duty.
Call of Duty 2021 has previously been referred to as Call of Duty: Vanguard by prominent leakers, so it's presumed that Slipstream is just a nickname to hide the game's true identity whilst it appears on Battle.net before having been announced.
These nicknames are a pretty common part of Call of Duty history. Last years' Call of Duty Black Ops: Cold War was nicknamed "The Red Doors". Before that, Modern Warfare was referred to as called “Pavelous”, World War 2 was called “Storm Flood” and Infinite Warfare was referred to as "Greentables".
Since being spotted on Battle.net, Slipstream has also been spotted on PSN. Over on Twitter, PlayStation Game Size Tweeted out an image of the Slipstream logo and referred to it as the Call of Duty 2021 Alpha. It's apparently 35GB, although there is no release date attached to it.
With Xbox being named as the official console of Battlefield 2042, it's likely that Call of Duty will once again take to Call of Duty, which is likely why it's appearing on PSN so early and not the Microsoft store.