The problem for GA Republicans is not DeKalb County which the Dems and Obama have maxed out, but the fact that the suburbs around Atlanta (Cobb/Gwinett/Henry County...) are trending heavily Democratic. If this trend continues, the rural Republican voters won't be able to outvote the Atlanta Democrats and Georgia will become the next Virginia (a blue state because of more diverse suburbs).
But the outer suburban counties such as Cherokee, Forsyth, Hall, and Walton are growing rapidly. They are turning out huge Republican majorities that are easily countering the ongoing changes in the city of Atlanta and the nearer suburbs. And they vote in much higher levels than the Democratic target voter does.
And the continued rural swing to the Republicans makes it hard for me to see Georgia change as rapidly as Virginia did. The 2014 elections in Georgia reflected that. As a Democrat, I'm disappointed!