Fortnite has evolved from a standard battle royale to an ever-changing platform that allows players and creators to live out their wildest fantasies on the island. Epic Games is the ultimate creator, adding new events and items to the game every two weeks. However, come content for the battle royale eventually gets scrapped or pushed to a later date, and it looks like portals are one of those features.
According to Fortnite data miner and content creator HYPEX, the devs have been working on working portals since at least Chapter Two, season five. That season had the focus on the Zero Point, and the portals would have likely been some form of Zero Point energy manifestation.
Epic was planning a portals game for Ch2S5, but it would be delayed once more due to a concept by Epic employee "Brelan Gale" @SentinelCentral
HYPEX stated that Epic is working on a portal feature for this season, likely in conjunction with the Reality Saplings and their Zero Point energy consumption. The portals appear to be fairly standard round gateways that will allow the player to go from one place to another. There are also illustrations showing the progress of the portals' opening and closing.
The purple variation almost looks like Zero Point energy that you can see coming from the island and water sources. This is stunning to look at, but it could be that there will be dangers starting next season. Whether or not portals will be introduced is yet to be determined, but it would make for a great crossover for the Valves Portal series.
Although we haven't seen portals in Fortnite yet, it appears that the developers have been working on them for the last few years. The mechanic may have easily been reworked, or fans might see it again in a future update.