I did want to give some detail on what the definition of a party based game was since there seems to be some confusion. In specific terms you will be creating and customizing four Rangers at the start of the game and typically you would give each of them different skills to create experts in certain fields. Skills in Wasteland range from lock-picking to bomb disarming to even toaster repair. This creates the dynamic of having players taking very different approaches to exploring the world. In addition there will be three slots for non-player characters to join the party. They will be similar in most respects to a player created member except you will not have 100% control over them. They will have quirks that could range from momentary indecision with them not firing their weapons at an opportune time, to being trigger happy and wasting ammo or even stealing from your characters. This opens up a wide range of possibilities on which NPCs you decide to have join your ranks.
And while we have brought Obsidian into the mix, I think it is important to note that this is my baby, and I will be producing it and managing the programming here at inXile. There seemed to be some confusion on whether it will be a joint production, but the main facets of our involvement are with the use of their tools for asset integration and the design talents of Chris Avellone. Part of the charm and variety of Wasteland 1 came from the way different designers would approach their areas, and I wanted the same dynamic again. Only this time we have added the brains of Chris into the mix, and I am betting he will add ideas to Wasteland 2 that would have never been in the game otherwise.
Update confirms: 4 ranger party, 3 followers. Top-down exploration with isometric town map and combat envisioned. Turn-based combat mostly taking inspiration from Jagged Alliance and the like. Story set right after Wasteland, starts you out as Ranger recruits playing in the area of the first game, later has you going into California to establish a new base.