We suspected a few days ago EA were planning something with Steam, and it seems now all has been officially confirmed, as EA titles will be returning to Valve's digital store, starting with Star Wars Jedi: Fallen Order.
Fallen Order will release on November 15th, and is listed and available for pre-order on Steam right now. More games will be coming from EA's catalog, though, including FIFA 20 and Battlefield 5 over the coming months and into next year.
The good news is that there'll be no disparity between Origin and Steam owners, so you'll be able to play online together and enjoy all the same features.
Interestingly, EA Access will also be coming to Steam, the first such subscription service on Valve's platform, which will let you gain access to a decent selection of EA's library for a monthly fee, as well as discounts and exclusive demos.