Battle Royale games are very much trending right now, and every major developer and studio has at the very least looked at the genre and their own games to assess whether or not the mode might be a fit for them. One development team that has done just that and decided against adding the mode to their game is Ubisoft Paris.
Responding to a question posed by a fan, a short statement was published on the official Ghost Recon Twitter that dismissed the idea, suggesting that it simply wasn't possible given the technical challenges involved and the structure of the game:
We understand the allure of the Battle Royale game mode and while it may seem like a natural direction for Ghost War. However, it would involve changes in the game structure and technical challenges that are simply impossible to undertake right now.
We recently heard word of some sort of Battle Royale mode/game in the works over at Massive, another Ubisoft team, so it seems that at the very least that the publisher is among those looking at the genre.