Via [url=https://steamcommunity.com/games/CSGO/announcements/detail/674006995886407686]the Steam Community[/url]:

[quote=Valve][b][u]PREMIER[/u][/b]
- Updated the map selection process to give players more opportunities to play maps they've been learning.
- Map selection process:
- Team 1 picks one map
- Team 2 picks two maps
- Team 1 picks a final map.
- One of the four maps will be randomly selected and the match will begin.

[b][u]RUSH[/u][/b]
- Rush is a fast-paced queued 3v3 game mode.
- Players battle through a series of battle arenas to reach the opponent's castle and win the match.
- Battle arenas are randomly selected for each match, so no two matches are the same.
- Control the tower when you eliminate the enemy team (or time expires) to win the round.

[b][u]GAMEPLAY[/u][/b]
- Players can now reload silently (but slowly) by pressing and holding the reload key.
- Un-scoping a sniper weapon no longer produces a sound.
- Globally increased visual clarity and improved fidelity of bullet impact decals.
- ammo_grenade_limit_total setting now also enforces the total number of grenades a player is allowed to purchase in a round.
- Chickens now take damage from the Zeus x27.

[b][u]SETTINGS[/u][/b]
- Crosshairs have been updated to be resolution independent.
- A new "Crosshair/Scopes" tab is available in the Settings menu, and includes updated crosshair settings.
- Added new crosshair styles
- Updated the default crosshair to "Dynamic Quad," which better represents weapon accuracy.

[b][u]ENGINE[/u][/b]
- Updated engine code to the latest version of Source 2.

[b][u]MAPS[/u][/b]
[b]Ancient[/b]
- Fixed holes in world in Long A Main Hall.
- Adjusted door geometry and grenade clipping inside Jaguar.

[b]Cache[/b]
- Some gap fixes and clipping adjustments around the blue doors in Mid.

[b]Mirage[/b]
- Reinforced scaffolding by balcony in A site.

[b]Train[/b]
- Blocked pixel gap in crates on bombsite A.

[b][u]MISC[/u][/b]
- Added ability to set a "Clan Tag" for players who are members of Steam Community Groups. You can adjust your Clan Tag from your Player Profile.
- Added support for applying stickers to C4.
- The Starjunk 95, Industrial Sunset Memories Music Kit is now available for purchase in standard and StatTrak versions through the STORE tab.
- Halftime scoreboard stats should now fully reflect the results of the previous round.
- Fixed a case where players could avoid a kick ban.

[b][u]WORKSHOP[/u][/b]
- Added "minimap_volume" entity which enables a custom minimap image when a player is within the volume.
- Added "sky_camera_volume" and "sky_camera_volume_target", which enable custom location-specific skybox rendering.
- Added "point_deathcam_bounds" entity that constrains the player death camera.
- Added "env_shake_volume" entity that allows camera shake only within a specified volume.

[b][u]SCRIPTING[/u][/b]
- Added CSRadarPoint entity.
- Added CSObservablePoint entity.
- Added AddTeamMoney API method.
- Added OnPlayerTeamChanged callback.
- SetDialogVariableString now accepts a localization string.[/quote]

Rumor has it:

- [b]Size is close to 5 GB (with Workshop Tools installed) - data capped users should take action now[/b]