The release date of Poe 3.15 is July 16, 2021, on PC, and July 21, 2021, on Xbox and PlayStation.
Note that this release time is subject to change, we can get the exact date on June 24.
The latest announcement on the official site reveals that patch 3.15 is planned for some time in mid-July, which will bring with it a new League, new rewards, and all of the associated elements of a new expansion launching in the middle of the summer.
The Path of Exile Ultimatum league will end 5 days before the start of the new league, which means we are about to leave the current league.
If you are looking for exact dates, these have not been announced yet, but you don't have to wait too long to learn more details. The developer plans to release all content, including the game name and game mechanics, through a live broadcast on June 24. So, stay tuned for more information that will appear later this month, and make sure to achieve your goals as early as possible in the current league.