Correct. In order for the exotic to drop you need the correct expansion/season. For example, the 6 new exotic armor pieces require the Witch Queen DLC to obtain from Lost Sectors. When the season changes to whatever follows Season of the Risen, you will need that Season to obtain any new armor exotics from Lost Sectors. Once the Destiny year changes (with the next expansion) you will only need the Witch Queen DLC for these exotics as the season passes will be removed. An example of this would be any exotic armor from Season of the Lost now just requires Beyond Light to obtain, as Season of the Lost is no longer a part of the game.