PVP
Throughout the holonet entry on Balmorra, there is constant reference to the fact that the planet has been a never ending battleground, where Republic and Sith forces have been clashing since the Treaty of Coruscant. The lore reasons being that the planet is of strategic military importance, both in location and production. However, there is a much more important hint buried in this entry: PVP.
Now, years after the treaty, a regrouped and rebuilt Republic is testing the limits of their fragile peace with the Empire, sending back the reinforcements they had pulled off the planet years before. - Holonet entry on Balmorra
The planetary description is littered with skirmishes lasting up to when The Old Republic takes place. Additionally, this is the first zone where both Sith and Republic forces seem to be equally referenced. Which, in turn, makes Balmorra the first promising location for all of those who have been waiting for signs of how the promised PVP might be implemented.
Beyond the actual entry in the holonet, there are situational clues strewn around the official website pointing at this planet being used by both factions. With all of the other locations being linked to only to one side or the other, this fact alone implies that BioWare is treating this planet a little differently then the rest we've seen.
NPCs and Architecture
Colicoids
One of the new pieces of concept art released with this Balmorra blitz mentioned "mutated Colicoids" located in "Bugtown". Closer to the time period of the movies, the Colicoids design and sell the droidekas first seen in The Phantom Menace, as well as joining the Sepratist Movement later in the timeline. These creatures have a destinctive defensive maneuver which invloves rolling themselves up into a ball.
What is not currently known is what effect being "mutated" will have on the Colicoids. They are considered to be an intellegent species with their own language and engineering abilities, but this could be drastically different from the Colicoids players will be encountering on Balmorra. Being 3000 years prior to the movies, as well as being mutated in some fashion, these could end up little more then feral insects
Balmorrian Soldiers
A small, underground Republic force was left on the planet to aid their Resistance, but the Balmorrans knew the truth of it; they had been abandoned. Even so, the Empire was still unable to take full control of Balmorra. - Holonet entry on Balmorra
In the intervening years, between the signing of the treaty and when The Old Republic takes place, Balmorra was able to maintain it's independence in the face of constant Sith assault with little, if any, help from the Republic. While it's uncertain whether this is from their biological forces or droid forces, the fact remains that the NPCs on this planet will be justifiably battle hardened by the time players get to first step foot on the planet
Planetary Defenses
Adding to the war-torn nature of Balmorra, nearly every screenshot and clip has a horizon full of large artillery pieces and other weapons of war. It's unknown how many of these will be static objects and how many will be moving and active, but they certainly do add a unique feeling to the planet. They could also being hints at possible objectives players may encounter through either PVE or PVP play.
One of the screenshots, in particular, show a couple of planetary defense ion cannons nestled in the landscape of Balmorra. These cannons were first seen in The Empire Strikes Back, defending the rebels fleeing Hoth from the Imperial blockade. Beyond being a nice nod to fans of the movies, these cannons certainly invoke a feeling that the battle being waged on Balmorra is much grander in scale then what we've seen in many previous MMOs.
Unfortunately we will have to wait and see exactly what is in store for gamers on this war-ravaged planet. Until BioWare says otherwise, everything covered in this article is simply spectulation and should be treated as such. Whether Balmorra ends up being PVP, PVE or both, it appears to be an interesting and important location for the story of The Old Republic.