On March 10th 2018 Epic Games tweeted out saying that cross-play will now be supported between Xbox/PS4/PC/Mac/Mobile. This is big news for Fortnite, mainly because previously players on Xbox were not able to connect with other players on different platforms. People were getting scared that if Fortnite did not support cross-play with PS4/PC/Mac/Mobile that Epic Games would stop supporting the version on Xbox. This was sort of like the "better together" update for Minecraft, in which the developers had originally stated that Minecraft on Xbox would no longer receive updates in the future. Lucky for Xbox enough people complained and support was given back to the version.
Here is a link to the article : https://www.epicgames.com/fortnite/en-US/news/xbox-cross-platform-fortnite