Hmm. I thought traditional SB soteriology subscribes to exclusivism. Putting aside special cases (e.g. those who die before the age of reason), traditional SB soteriology says those who live and die outside the pale of the Gospel cannot be saved. That's a presupposition of traditional SB foreign missions. Faith is Christ is necessary for salvation. So anyone cannot be saved.
So the book would only make sense if it represents a shift from exclusivism to inclusivism, viz. Jerry Walls, John Sanders, Gabriel Fackre, Clark Pinnock.