I know this site's userbase doesn't care a whole ton about Fortnite but this is still interesting to note as it looks like Fortnite could potentially be one of the first multiplatform games to have a skin based of characters from each first party console maker.
So first off the Kratos is is already in the game right now and it should be noted the skin isn't exclusive just to the PS4 and PS5 versions of Fortnite, it's also available in the Xbox, Nintendo Switch, and PC versions of the game. So yep you can essentially play as a first party Sony character on any platform. And as for the rumors, it looks like Master Chief will be coming next as dataminers have found Halo items are already in the game files. Obviously the question now is, will there be a Nintendo rep? Right now rumors suggest it might be Samus Aran from Metroid . Now the reason why Samus is speculated even though no hard proof exists yet is because apparently the theme for the current Fortnite season is multi-dimensional crossovers with "hunters" of some variety. For example Mando from The Mandalorian has already been put in as one of the major skin releases for this season of the game, and Kratos, a man who hunts down mythological gods, is now in the game, and Master Chief might be a slight stretch on the "hunter" part but you could argue he is the one who hunted down the Covenant leaders. So for Nintendo the one that makes the most sense is Samus, as she is a bounty hunter. Plus I feel like Nintendo might be more likely to give the okay for Samus to be shooting assault rifles and pistols than they would someone like Link or Mario (and as a reminder, in Mario x Rabbids the weapons Mario and co used were energy beam weapons, which aren't held to the same scrutiny as weapons that fire bullets).