The technology can already be found in Apple's Swift Playgrounds code-learning app for the iPad, according to a post on Reddit. An extended menu in the app offers a "Broadcast Live" option — selecting this prompts users to pick from outside apps that allow broadcasting.
At WWDC Apple introduced ReplayKit, a framework that will support both live broadcasting and saving videos for later viewing and sharing. The technology is primarily gaming-oriented, reflecting the popularity of games on broadcast-ready services like Twitch and YouTube.
From the beginning Apple mentioned that Swift Playgrounds would support live streaming, but the initial version of the app didn't include the option.
The finished version of iOS 10 isn't expected to arrive until sometime this fall, most likely September. With major iOS releases, Apple will often add promised features over the course of several betas, giving it time to test things and flesh them out.