When Jim Dale read book 4, he claimed to have voiced more than 125 characters. But in the recent Wall Street Journal interview (see a couple posts below), and on his personal web site, he says he did 134 for OotP. Doing the math we can see that that's nine more voices. Possibly not new characters, but at least characters we know of that haven't spoken before. But also, there are characters such as Cedric who were counted in the 125, who will not be speaking, so that means that there will be even more than 9.
