Holy sith of patch notes there are a LOT of changes coming in 4.0!
Hightlights posted below, please check out the link for the full notes!
Knights of the Fallen Empire*
*Knights of the Fallen Empire content is only available to players who are eligible for the four Knights of the Fallen Empire subscriber rewards by having been a subscriber on August 10th, August 31st, September 30th, and October 19th, 2015. All other subscribers will be able to access the content on October 27th, 2015.
Highlights
- All classes can now reach Level 65!
New Ongoing Storyline! Knights of the Fallen Empire begins an epic, new storyline at level 60, with nine, action-packed Chapters. Regular Chapter releases continue the story starting in Early 2016. (Subscription Required)
Start at Level 60! Jump right into the action of Knights of the Fallen Empire with the option to begin the game at level 60! (Subscription Required)
New Player Tutorial! Chapter I introduces you to your class’s abilities and eases you into combat while the story unfolds. Veteran players can disable the Tutorial via the Menu.
New Planet: Zakuul! The new seat of power in the galaxy! Skyscrapers reach toward the stars while surrounded by a vast and savage swamp.
New Companions! Unlock new Companions over the course of the first nine Chapters of Knights of the Fallen Empire.
Begin your Alliance! Continue your adventure after Chapter IX by recruiting Companions to grow your Alliance.
New Flashpoint: Star Fortress! Conquer the new Flashpoint and liberate the Galaxy from the grasp of the Eternal Empire!
- New 1-60 Leveling Experience! Leveling from level 1 has never been more exciting! You can now reach Level 60 by doing Main Story Arc Missions and Planetary Arc Missions.
Reworked Primary Stats! The four primary stats Strength, Willpower, Cunning, and Aim have all been replaced by a single stat called Mastery. For this and other stat changes, see the Classes + Combat section below.
New System: Level Sync! Adventure with other players with Level Sync! Get level appropriate Experience and Mission rewards while grouping with other players on the core worlds, while retaining all of your abilities! Those womp rats won’t know what hit them!
Legacy-Wide Datacrons Now Live! Found Datacrons now grant stat bonuses to every character in your Legacy! You can track your Datacron progress in the Legacy window.
Flashpoint and Operation Revamp! Flashpoints and Operations have been revisited and updated! New Modes are now available for many older Flashpoints, and many others are now available at max Level. See the Flashpoints + Operations section for full details!
Ranked Arena Season 6 has come to an end! Season 6 has come to a glorious conclusion! You can use your Season 6 Tokens to purchase rewards from the vendor in the Combat section of either Fleet.
Nimue De Danann 
