Actually the 3DS name is just a placeholder and isn't confirmed. Like the Wii was called Revolution. As for it being a new DS i think it will be. The DS series has sold like crazy and I think it will be an improved version that does 3D gaming justice, assuming Nintendo doesn't drop that...
As far as I know and it has been confirmed by Nintendo, there is another DS to be coming out but it will have an accelerometer which means it will be like a mini version of motion control. People who have an Ipod nano may know of similar technology used for the sideways flip and the maze game on...