Fortnite is everywhere, it’s on PC, Xbox, PS4, Switch and even on iOS and Android now. I can’t recall any other mainstream game which is so diverse in choice of platforms.
One of the advantages of having so many platforms, is to bring people together through cross-platform gameplay. Because not everyone is on the same console or computer, this helps friends from different platforms play together and enjoy the game.
But this approach has a few problems, generally a player on PC using mouse and keyboard will be more accurate than a player on a contoller, this might give undue advantage to PC players when playing against consoles. This in turn might compel many PS4 and Xbox players to use mouse and keyboard for themselves making it even more difficult and unfair.
That is why Epic Games, the developers or Fortnite have decided to segregate mouse and keyboard players differently from the main pool. That means players using MKB on any platform will be matched with each other. This also extends to an entire squad in-game, if even a single player is using MKB, the entire squad will be matched with the mouse and keyboard pool.
Although the Xbox One doesn’t have MKB support yet and PS4 barely supports it, there are many players who still use an adapter like Xim to emulate a controller , this would still remain undetectable.
In the State-Of-Developement blog post by the devs, Epic also announced the introduction of a competition system. They also announced the introduction of 4k resolution support on 4K TVs for PS4 Pro owners. There will also be a lot of performance improvements in the 50v50 mode of the game. These changes don’t have a tentative release date, but many of them will arrive soon.