Thanks to Giskler from TheCivForum, there is an asset file hinting at either future contents or scrapped contents:
4th Age: Atomic Age
Civs: Iceland, Tonga, Ottomans, Maori, & Pirate Republic
Leaders: Edward Teach, Sayyida al Hurra, Whina Cooper
Wonders: Asia wonders
Why should you trust this? This file includes all 8 previously-leaked civs for Civ7.
Why shouldn't you trust this? The Pirate Republic seems both too brilliant and too stupid to be true.
https://forums.civfanatics.com/threads/asset-file-hinting-at-future-and-or-cut-content.695000/