Austen Goslin, Polygon:
According to a tweet from the Fortnite Status Twitter account, which keep players up to date on the technical side of the game, upgrading to the new Apple operating system could result in Fortnite being deleted from your phone. The iOS upgrade will reportedly ask some users if they’d like to “Temporarily Remove Apps to Install the Software Update” and, if they select yes, Fortnite is likely to be deleted.
Apple does not explain how iOS selects which apps to temporarily remove in order to free up space, but an educated guess suggests that it removes the largest apps first. Games like Fortnite have massive bundle sizes, so that’s why it is likely to be removed for an update. Apple’s UI copy indicates that it is temporary but, because Fortnite is no longer on the App Store, it is effectively permanent.
Speaking of which, there does not appear to be a way to transfer Fortnite from one iPhone or iPad to another. Both local and iCloud backups exclude App Store data, and there is no other way of transferring an installed app from one device to another. That probably won’t impact sales of this year’s iPhone models, but I imagine it will upset a good many players.