I'm not sure about everything planned, but here are a few things I know we will see:
Check this forum post for details:https://forums.embersadrift.com/index.php?threads/anniversary-event-play-the-game-for-free-starting-oct-13th-to-nov-5th.4169/
More details here:https://forums.embersadrift.com/index.php?threads/state-of-the-game-1-year-anniversary.4172/
And if you aren't familiar with Embers Adrift, it's a little different than most modern MMOs (a welcome thing, in my opinion). It clearly takes inspiration from old-school MMOs like EverQuest. There are no cash shops or microtransactions, so if you see someone with a cool weapon or piece of gear, they didn't purchase it with real money... they earned it. The game is exclusively PvE; there is no PvP (again, a welcome thing). Embers Adrift forces you to figure things out for yourself and to interact with the community. While soloing is an option, adventuring with a party is a much more rewarding experience.
So, the game is unapologetically niche and won't be for everyone. That said, if any of the above sounds interesting, or if you're even a little curious, I encourage you to take advantage of this generous free period and see for yourself. I'm guessing that a couple of dungeon runs through Central Veins and getting a character up to level 20 or so will convince more than a few folks that this game is a diamond in the rough, as it did me.
If you end up giving it a try, look me up in game! I'm almost always on my primary character Meeks, a level 39 Sentinel.