Dissida Duodecim (Dissidia 2) Announced!

Release dates:

JP March 3, 2011
NA March 22, 2011
EU March 25, 2011

Confirmed Roster:

FFI: WoL, Garland, Chaos
FFII: Firion, Emperor
FFIII: Onion Knight, Cloud of Darkness
FFIV: Cecil, Kain, Golbez
FFV: Bartz, Exdeath, Gilgamesh
FFVI: Terra, Kefka
FFVII: Cloud, Sephiroth, Tifa
FFVIII: Squall, Ultimecia, Laguna
FFIX: Zidane, Kuja
FFX: Tidus, Yuna, Jecht
FFXI: Shantotto, Prishe
FFXII: Vaan, Gabranth
FFXIII: Lightning

New Mechanics
The mechanics of the battle system include "EX Mode" and "Assist." EX Mode functions exactly the same as the first game by collecting EX Cores around the battle map to fill up the gauge and transform the character into a more powerful state, which allows players to perform a powerful EX Burst attack should an HP attack land during EX Mode. The Assist system is a new element to the game which allows the player to summon an additional ally into battle to either assist in attacking the enemy or defend from an oncoming attack. It is performed using the Assist Gauge, which is built up by using Bravery Attacks.

Both modes are supposed to balance each other, because when an EX Burst is executed, the opponent's Assist Gauge is reduced to zero.
The three main countering systems are Assist Breaks, EX Breaks and EX Revenge. An EX Break is performed by stopping an opponent's EX Mode through the use of an Assist attack which forces the opponent out of EX Mode, additionally passing the opponent's Bravery points to the player. An Assist Break is performed by attacking the opponent's Assist character, causing him/her to be unable to call out the Assist character for a brief period; this also passes the opponent's Bravery points to the character. Lastly, EX Revenge occurs when trying to activate EX Mode while being attacked. While in the first game it would simply halt the opponent's attack, it now slows down time allowing the player to pummel the opponent instead, though it sacrifices the player's ability to use an EX Burst as it uses up the entire EX Gauge.

The biggest change is within the single-player story mode of the game, taking place on a traditional-styled Final Fantasy world map, with players being able to experience a story while exploring a world with scenarios and events taking place as the story progresses. Players will traverse the 3D world map with three-character parties, with players being able to interact in conversations with the characters. When roaming the map, players will encounter enemies known as "Manikins"; when attacked by an enemy, players will be transported to a battle map where battles will take place. There will be shops on the map which are specially marked. The story mode is also party based, similar to the story progression of Final Fantasy VI. In certain scenarios, parties will be predetermined, but in most cases players are free to select their own party. Alongside the game's new story mode, the game will also include the first game's story which will be remade with the 3D world map as well as additional elements added for the new storyline. Tetsuya Nomura, producer and character designer for the game, has said that both storylines played together would result in approximately 60 hours of gameplay