Yep, in the usual Firaxis move of no publicity at all, they introduce the Maya, the first of two Civs this month (next week!) that will be available as part of a year long season pass with 6 updates from May to next March.
Plus free updates or something.
https://civilization.com/news/entries/introducing-the-civilization-vi-new-frontier-pass-first-dlc-launches-may-21-2020/
The 'new game mode' this month is apparently 'Apocalypse Mode' which adds two unspecified disasters.
Civ#2 Alongside the Maya is Gran Columbia, the famous Spanish colonial nation known by everyone that... lasted all of 12 years. Truly, a civilization that stood the test of time.
Ethiopa comes in 'July's' update (assuming they can keep to this Pack-every-two-months schedule). And everything else is a complete mystery!
Pre-order (eventually) gets you new leaders in the shape of skins for Old Leaders. Rowdy Teddy and Luxurious Catherine! Couldn't have done a different American president or French monarch, because reasons.
Various other updates and changes will happen inside and outside the season pass, but they aren't going to tell anyone what any of it is, because they want the money first.
Guesses are about $40 for 8 Civs total + one spare leaders, 6 'game modes' (which aren't scenarios, but checkboxes to enable each 'mode' in normal games, and a smattering of new city states, resources, a district and infrastructure (update 2) and ???
Plus the threat of new maps and 'balance changes'
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In case it isn't clear, I'm not a fan of buying mysteries nor splattering little bits of content out over a year. I'm really not a fan of the lack of information, especially 'buy first, find out whats inside the mystery box second'