The HK-55 helmet and weapons will not be from a Cartel Pack. Not sure what's with the red helmet.

Subscriber Rewards

HK-55's Helmet

Subscriber Reward

HK-55's Helmet

Subscriber Reward

HK-55's Helmet

Subscriber Reward

HK-55's Blaster Pistol

Subscriber Reward

HK-55's Blaster Pistol

Subscriber Reward

HK-55's Sniper Rifle

Subscriber Reward

HK-55's Sniper Rifle

Subscriber Reward

HK-55's Vibrosword

Subscriber Reward

HK-55's Vibrosword

Subscriber Reward

2V-R8 Customization - HK-55 Inspired

Subscriber Reward

C2-N2 Customization - HK-55 Inspired

Subscriber Reward

New Cartel Market Items and Decorations

Advanced Turquoise Crystal

Dasta Emissary

Droid Companion- QO-77

Jedi Strategist's Armor Set

Marsh Hunter Acklay

Oberle Siren

Tempted Apprentice's Dualsaber

Tempted Apprentice's Lightsaber

Tempted Apprentice's Shoto

Relentless Hunter's Armor Set

Wartime Ambassador's Armor Set

Zakuulan Inquisitor's Armor Set

Terrorclaw Raptor

Arrangement Satele's Camp

Medical Centrifuge

Odessen Weapon Forge

Statue of an Ancient Jedi

Zakuulan Temple Torch

Shadow Corsair

Triumphant Predator's Armor Set

New Loading Screens

New Chapter 12 Weapons

These weapons are all 204 rating and unmoddable outside of the colour crystal. All class variations use the same model and just have a different name. These weapons will grant you special abilities in a special encounter in the future based on the choices you make throughout Chapter 12.

Attuned Assault Cannon

Attuned Blaster Pistol

Attuned Blaster Rifle

Attuned Lightsaber

Attuned Saberstaff

Attuned Sniper Rifle

Things of Note

• You can now set mounts as favorites by right clicking them in the ability panel.
• The random mount ability will now only pull from the list of mounts you have set as favorites.
• Looks like one of the upcoming sub-rewards will be C2-N2 and 2V-R8 HK-55 inspired customizations.
• Rest of Chapter 12 dialog is now in the client.
• A few cutscenes from Chapter 16 now have their dialog present in the client.
• Other spoilers available in the detailed changes for those that want them.
• Lots of work done on the Eternal Championship.
• The HK-55 helmet is now Bind on Pickup rather than Bind on Legacy.
• Theron Shan has been wearing the same outfit since he was a child.
• No class changes.
• No sign of Ranked Season 7.
• Guild ship max hooks when fully upgraded increased to 800 from 700.
• Guild ship max hooks without unlocks increased from 200 to 300.
• Several old armour sets from class quests look like they are getting added to a vendor on the fleet. All adaptive and BoL.
• As pointed out in the comments there's a "tuning mod" item. It's description indicates it allows you to add visual effects to your weapons. Currently it shares the same slot as colour crystals. It's labelled as a rare cartel market item. This is probably a distant feature rather than something we will see in 4.4. Doesn't appear to be too much data on this feature currently. When it is released I would expect it to occupy a different slot.

In-depth Changes (Contains heavy spoilers)

Changed Abilities
Changed Achievements
Changed Areas
Changed Codex Entries
Changed Collections
Changed Companions
Changed Conquests
Changed Conversations
Changed Decorations
GOM Changes
Changed Items
MTX Changes
Changed New Companions
Changed NPCs
Changed Quests
Changed Schematic Variations
Changed Schematics
Changed Ships
Changed String Tables
Changed Strongholds