Ubisoft is looking to drastically tighten up the map pools for both casual and ranked playlists in Rainbow Six Siege in an effort to make the game easier to learn for newcomers and more competitive in ranked. The new map pools will cut three maps from ranked play, while the casual map pool is also getting reduced it will receive seasonal rotations of maps to keep things fresh, but learnable.
So, what are the maps being cut from the ranked map pool? Fortress, Theme Park, and Hereford are all out when the Rainbow Six Siege Ember Rise release date rolls around. The newly reworked Kanal will be added to ranked to make up for the deficit, but this brings the ranked map pool much more in line with the maps played in competitive. Theme Park will likely return as its slated for map rework at the end of the year, but there are currently no plans to reintroduce Hereford or Fortress.
Another change that will make the transition to ranked a lot easier, especially when it comes to learning each map is the addition of an unranked playlist, which take the same ruleset and map pool of ranked without the threat of getting deranked.