Season 3 is coming to an end soon, and Season 4 is on the horizon. At the end of each ladder season, leagues are “locked” which means players can no longer be promoted or demoted out of their current league or division, and bonus pools will stop growing. That’s no reason to quit playing: even after leagues are locked, players will still be able to play out their remaining bonus pool and compete for standing within their divisions until the end of the season two weeks later. The match-making skill ratings which determine league promotion and demotion will also continue to update during the lock, so games played during the lock still count toward league placement in Season 4.

The Season 3 lock will go into effect the week of October 10th. Season 3 will officially end, and Season 4 will begin on the week of October 24th. Season milestone rewards will be locked in at this time, and bonus pools will start over. Hidden skill ratings used for matchmaking and league placement will carry over from the previous season, so players who have completed placement matches in a previous season will only need to play one new placement match after Season 4 starts.

Beginning with Season 4, there are two changes coming to future ladder seasons:
Each season will now last for approximately two months
Grandmaster league placement time will be reduced to one week (from two weeks) to account for the reduced season length