I continue to think that 8km will make the woman's race worse. It will be a less interesting, less competitive race. Look how few runners can even stay with a quick pace in the NCAA 10,000 (when it goes quickly).
And, women get hurt at higher rates then the men, even though they are only doing 5 and 6km; at 8km it would be worse.
Finally, I do not remember a lot of coaches pushing for the distance to be increased to 8km, much less 10km. Those are the people that know the athletes best.