Cleveland's population peaked at 915k in 1950. The population loss isn't anything new and has slowed down dramatically after the recession. The region is still the 16th largest in the country...people might be leaving the city but there are plenty who are staying in the region. The regional population is only about 30% off of its historical peak in 1970.
Regardless of the numbers, none of this new and suddenly making NE Ohio football talent irrelevant.