According to the IAAF Council Meeting Notes from this weekend, starting at the 2015 Beijing World Championships, "Mass participation races for men and women to be held at the same time of the World Championships marathon races."
There's no details in the article, but I wonder if this will work like the World Marathon Major races where the elite women start early and the masses start at the same time as the elite men. Or will they have completely separate starts for the World Champ races and mass race?
If they do start the men with the masses it could be pretty interesting if an elite who wasn't chosen for their country's team enters and ends up winning or placing very high. With the depth of Kenyan/Ethiopian marathoning this could easily happen.