Borderlands 3 is now officially confirmed for a September 13 release date on PC, PS4, and Xbox One. Gearbox is already touting the multiplayer features players can expect in the loot shooter, from split-screen local multiplayer to online cooperative play, but the Microsoft Store may have let slip a bit more information than Gearbox was otherwise ready to announce. The Borderlands 3 listing on the Microsoft Store included a note regarding the inclusion of "Cross-Platform Co-Op."
In the Microsoft Store listing for Borderlands 3, several features are listed individually under the sub-heading of "Categories." For example, some of these features include "4K Ultra HD," "Xbox One X Enhanced," and "Online Co-Op." After the listing went live alongside the Borderlands 3 announcement earlier this morning, "Cross-Platform Co-Op" was also listed as a feature for the game. However, that feature has since been removed from the list.
The implication being that Borderlands 3 may feature cooperative cross-play between the PC and Xbox One come launch, given that it's from a listing for the Xbox One version of the game. The possibility of PS4 cross-play isn't outside of reality, even if it's limited to PC and PS4, but can't necessarily be intuited by the Microsoft Store listing.
Or, just as likely, the feature was added by mistake and Borderlands 3 doesn't actually feature cross-platform co-op. While the possibility of cross-platform co-op is exciting, given the limited nature of cross-platform play in the current market it's perhaps safer to assume that this was an accident and not a hint at a real feature.
With the recommendation of maintaining healthy speculation taken care of, it's worth acknowledging the feasibility of Borderlands 3 featuring cross-platform play. Given Borderlands 3's now-confirmed relationship with Epic Games, both as an Epic Games Store limited exclusive and as a game built on the Unreal engine, it may very well feature the same technology Fortnite uses for cross-platform play. Epic previously confirmed that the "core features" required to share the cross-play tech would roll out mid-2019, so with Borderlands 3 launching in September then it's realistic for the game to utilize such a feature. Possible, but again, not officially confirmed.
Borderlands 3 releases September 13 on PC, PS4, and Xbox One.