Star Wars Galaxies 2 will most likely never happen, owing to the fact that SOE has publicly stated that it will never work on an MMO based on an external IP again. Whether that's true or not, if somehow this project were to be conceived, here are the changes from the original that I'd personally want to see in a sequel.
Modern Graphics Engine
This is the most obvious one. My personal choice for SWG2's engine would be Unreal Engine 4, owing to its extremely impressive technology. The “Infiltrator” demo video for UE4 shows that it would be perfect for the realistic art style of the Star Wars: Galaxies franchise, as compared to the more stylized art direction of Star Wars: The Old Republic.
A Return to Skill-Based Character Progression
Like most SWG veterans, I lamented the loss of the skill tree progression system when the New Game Experience took over. With SWG2, I'd want to see it return with a vengeance. Particularly, I'd like to see the depth and breadth of trees expand, allowing for greater freedom than even the original. Several aspects of the Star Wars universe were never fully explored in the first game, or were only given light treatment, such as slicing or smuggling.
More Player Races
The selection of available races in the original was good, allowing for most of the popular choices. I would like to see the Togruta, Chiss, and Devaronian races make a core appearance in SWG2. I'd also like to see droids as a player race, though that might be too complicated to balance against other races' gameplay.
Bigger Worlds
The original SWG planets were pretty big, but they frequently felt empty. The expansion worlds had stronger design, but felt smaller. I'd want to see planets in SWG2 be more expansive than the original SWG planets, but have more points of interest throughout each. For example, the planets in the first SWG felt a lot like the same planet given a different skin each time. While I don't want quests to provide a meta plot, I would like to see localized content that gives each world its own character.
Greater Freedom of Movement
Let's face it, movement was pretty horrible in the original SWG. You couldn't jump or fly over obstacles, and it was completely possible to walk straight up a sheer cliff face. While we don't necessarily need the full parkour aspects of EverQuest Next, I do want the ability to jump over things, be prevented from walking up impossible surfaces, and be able to climb, swim, and otherwise move as a person should be able to move.
Atmospheric Vehicles
I know these were added to the original SWG, but it came only in the last few months of the game's life. Given how important they are to the Star Wars universe in general, it would be a crime not to include these from the beginning in SWG2. I want to be able to bullseye womp rats in a T-16, over take a cruise over the highlands of Corellia in my own YT-1300. I also want shuttle transports to actually have real transit time, and not be a wait-and-teleport affair like they were in the original.
Player Factions
While it was great to have Imperial and Rebel affiliations in the original, to really ramp up the sandboxy nature of Star Wars Galaxies, the sequel would need to have player factions. This is particularly important if the game is set in a time period after the fall of the Empire, where a billion new factions would be vying for power. I see player factions being akin to massive alliances of Player Associations, rather than just an enormous PA. They'd also have to be able to influence planetary politics, like how Imperial and Rebel players were able to influence things towards the end of the original SWG.
A Player Exchange
Unlike the auction house format of current MMORPGs, I'd like to see something closer to the original vendor system in SWG. You'd be able to search available items on a local, planetary, or galactic level, as well as purchase them, but you'd need to physically travel to the vendor in order to pick up the item or items. This is important for two reasons: to encourage exploration and travel, and to support the possibility of player deliverymen - “FedEx” quests that actually matter. I want to have to travel to Tosche station to pick up some power converters.
Greater Visual Customization of Crafted Items
I liked that crafters could dye armor in SWG, but a sequel would need to take it to a new level. Item appearance should be further separated from item game mechanics than in the original. There is a vast variety of armor appearances in Star Wars, for example, and that should be reflected in SWG2. I don't want just a dozen different kinds of armor in different colors. I want several dozen, if not more. If World of Warcraft can do it, so can SWG2. Involving the Player Studio could help defray the cost of developing new models and textures for components of items.
Vehicular Combat
If we can fly in the atmosphere, we should be able to fight in it also. I'd want to see hover tanks finally make an appearance, among other things. If PlanetSide 2 can balance heavy armor against infantry, Star Wars Galaxies can do it too. This list could be even longer, but the above are my biggest wishes for a Star Wars Galaxies 2. How about yours? What would you want to see in a sequel?