FFG has a new article that spells out formats and their rotation schedule. Rotation is every 2 years about and it rotates out the oldest "Cycle" of Cards. An Example is that Awakengins through EAW will cycle out of standard play in the fall of 2018 or early 2019. The current 2 cycles will make up what is "Standard" Format play. In addition there is Trilogy play, which consists of product that is part of the most recent cycle released, this will start with Legacy Trilogy when Legacy launches. Last is Infinite which as the name suggests means everything is game to be used.
https://www.fantasyflightgames.com/en/news/2017/11/8/swd-what-lies-ahead/