Take a look at how the 3 Atlanta metro counties that Hillary flipped have changed over the last 4 elections. Gwinnett and Henry show a huge trend that will probably continue to be favorable for Democrats.
Democrat % of vote:
Gwinnett County, GA
2004: 33.44%
2008: 44.35%
2012: 44.56%
2016: 50.20%
Henry County, GA
2004: 32.84%
2008: 45.85%
2012: 47.81%
2016: 50.38%
Cobb County, GA
2004: 37.12%
2008: 44.67%
2012: 42.83%
2016: 47.93%
Edit: I'll also look at Fayette County, GA which is in the southern part of the metro. Trump won this county by a decent margin but it is also gradually shifting toward the democrats.
Fayette County, GA
2004: 28.29%
2008: 34.17%
2012: 33.61%
2016: 37.85%
Lets see GA Demograhics:
Gwinnett County:
2010: 44% White, 2015: 40% White
24% Black 28% Black
20% Latino 21% Latino
11% Asian 12% Asian
3% Other 3% Other
Cobb County:
2010: 56% White 2015: 53% White
25% Black 28% Black
12% Latino 13% Latino
5% Asian 5% Asian
2% Other 3% Other
Henry County:
2010: 53% White 2015: 47% White
37% Black 42% Black
6% Latino 7% Latino
3% Asian 3% Asian
2% Other 2% Other
Fayette County:
2010: 68% White 64% White
20% Black 23% Black
6% Latino 7% Latino
4% Asian 5% Asian
2% Other 2% Other
