The new game will be published by Paradox and is being developed alongside them. This is in contrast to Obsidian's previous game, Pillars of Eternity, which was crowdfunded on Kickstarter.
The new RPG uses the Pillars of Eternity engine (hopefully refined so it's not quite so much of a system hog) but is set in a whole new world. The premise is that a massive battle between good and evil has been fought, but evil has triumphed and the Dark Lord Kyros rules the world. Your character is a Fatebinder in the service of Kyros, but one who has free will of his or her own. The game will apparently explore, in true Obsidian style, the consequences of moral choices and violence. However, this will (apparently) be Obsidian's first big RPG made without any input from the mighty Chris Avellone, who has decamped to Larian Studios to work on Divinity: Original Sin II.
Interestingly, the game has a 2016 release date, meaning we should see it relatively soon. Which is bad news for those of us who are still one-third of the way through Pillars of Eternity with other games taking priority (ahem).