To see the teasers you'll need to find the monitor newly installed in the firing range. It will give you a series of challenges to complete. Once you're finished, go back to the monitor to watch the character teaser. Horizon will introduce herself as Doctor Mary Somers. She'll thank you for the data and tell the player that it'll come in handy when "we face you" in the games. Who the other person she's referring to is unclear. She appears to have a small drone companion so it is possible that that is who she's referring to.
Although there is no release date for Horizon yet, based on her "see you real soon" at the end of her message it is likely she'll release with Season 7 on Nov. 10.
The Champion's Edition will also be released at this time and will include unlocks for Caustic, Mirage, Wattson, Octane, Crypto, Revenant, Loba, Rampart, and the Season 7 hero, who will likely be Horizon, as well as 1,000 Apex Coins and seven exclusive legendary cosmetics.