Final Fantasy Tactics has been confirmed by Square the Nintendo DS. The current name for the Japanese title is Final Fantasy Tactics A2 Fuuketsu no Guurimore. Currently it is being developed as a sequel to the GBA game, Final Fantasy Tactics, making this an original title just for the DS. Not much more information is known but this is good news just the same. The Nintendo DS now has several RPG games on the way from Square Enix including Final Fantasy 12: Revenant Wings and Dragon Quest 9.
AMN will keep you updated.