I personally think they have the ability to add alot. Because within the SWTOR universe they have some much to expand on. Unlike other certain games that are ending the expanse of their lore. The SW universe has million of things that can be added.
Races:
-Mon Cal
-Wookiees
-Bothans
-Duros
-Rodians
-Trandoshans
-Hutt
and thousands of others.
Worlds:
-Naboo
-Geonosis
-Kashyyyk
-Felucia
-Bespin
-Endor
Classes:
This is alittle harder as they have basically got most of the "classes" you think of when thinking of Star Wars but just off the top of my head.
-Musician
-Beastmaster
-Engineer
Professions (Crew Skills):
I think there is a new limitless expanision to this. I believe first they would need to rework their current ones a bit. But here are a few ideas:
-Shipwright (Work on making ships for the new space expansion everyone is hearing whispers about)
-Furniture Designer (Create Furiture to help decorate the insides of your ship, future housing, and Guild Ships.)
And many more.
Space Combat:
Bioware is already confirmed new and way improved Space Combat and such, with the addition of Guild Capital Ships, this could bring a new meaning to PVP and World PVP and world conquering.
-Guild Ships: I think they should have it to where to effectivally run Guild Ships it requires a small number of people (5-7) to run them and man the weapons and such.
-Fighter Combat
World PVP:
In the future they will bring forth more reasons to World PVP, maybe increaseing Valor (or giving Valor) for killing an enemy.
-World Conquering: There should be a way one faction or another can conquer one planet or so.
PVP:
New Battlgrounds
Tanks, Turrents, etc inside battlegrounds.
This is just a small list of things that could and hopefully will be added. The content is there. Plus anything they wish to bring in with quests, classes, and storylines.
-Nalriem Qyan, Jedi Medical Corps.