Though it hasn’t yet been announced, a clip shown during the trailer for Epic Games’ GDC 2018 keynote revealed that the ‘upcoming feature’ mentioned is a Replay system!
— FortniteINTEL.com (@FortniteBR) March 21, 2018
Update: Here’s a Project Spotlight video from Unreal Engine featuring Ali-A’s hands-on experience with the Replay mode:
The feature will be coming “soon” to Console/PC, with no current news on a mobile release. Those at GDC 2018 will have a chance to try it in person at the Fortnite booth.
Using this new system, players will be able to watch back gameplay that has just taken place, allowing them to improve on their skills and record footage with more capabilities than ever before. Focal length, Camera Position and Aperture are just a few of the things you’ll be able to customize to create exciting Fortnite content.