Even though it's still a rumour at this point, it didn't take a rocket scientist to see it coming, what with Epic already porting Fortnite to everything they can get their hands on. However, it is said Save The World will have some changes.
Note that Fortnite: Battle Royale is coming as is, meaning that little, if any, changes will be applied before it hits the Switch. Furthermore, Save the World and Battle Royale may not be released at the same time.
Reportedly, the paid part of the Fortnite experience, Save the World, will feature content tailored specifically for Nintendo's platform. With the staple of the mode being the four player PvE co-op, it's not hard to see why Nintendo liked the idea.
Save the World should lend itself well to the Switch, allowing four player local play on the console. There were some rumours about the marketing side of things and how Epic and Nintendo planned to advertise Battle Royale for the Switch's stationary mode and Save the World as the on-the-move option, but that's still heavy speculation.
Despite Nintendo's apparent preference of Save the World, we all know what the Great Unwashed are clamouring for - Battle Royale. The mode will of course offer cross play and all the bells and whistles featured on Fortnite's PC, PlayStation 4 and Xbox One versions.
Source of the rumour is LeakyPandy, a.k.a. Vandal_leaks, who has already successfully foretold the Nintendo Direct presentation back in March. He did however point out that there are a lot of conflicting rumours swirling around and how the public should take them with a grain of salt.
Having said that, we can't say we didn't see it coming. Epic has been busy lately porting Fortnite to mobile, obviously with great success. Even though it's just cosmetics, the company has earned a pretty penny on Apple's Store and with Android on the way, it all seems rosy.
Furthermore, in spite of Sony's quiet grumbling behind the scenes, Epic seem to be the first company that insists on providing cross play for its players. It's safe to say that we'll be adding another platform to the cross play list now.