No need to panic ...
Any track event longer than 800m is usually only exciting the last 800m anyway. If we were to reflect back to 1960, which 5000m/10000m medalist would have been unable to be competitive in either 3000m or Marathon? 3000m is the perfect next event for aging 1500m athletes. In his salad days Lasse Viren was a strong two mile runner. It would have been great to see Viren, Miruts Yifter and other 5000m guys racing 3000m such as Ben Jipcho. This will actually be good for the Marathon. There will be no more 5000m/10000m gals/guys only choosing to specialize as a Marathoner in their thirties. Gals/guys are going to have to choose to specialize in Marathon at a far younger age.