In my humble opinion, North Carolina will become a reliable Democratic state - if that is to happen - around the same time as Georgia (and maybe even later). I maintain to this day that the Obama campaign made perhaps the best short-term decision (as all campaigns focus on; it's not their job to worry about long-term trends), but the DNC et al made a tragic mistake in not investing more in Georgia in 2008 & 2012. Let's look at the difference between GA & NC:
NC & GA D Share of Vote:2004: NC 43.58% D; GA 41.34% D
2008: NC 49.70% D; GA 46.90% D
2012: NC 48.35% D; GA 45.39% D
Tracking of NC & GA:2004-2008: NC 6.12 points D gain; GA 5.56 points D gain
2008-2012: NC 1.35 point D loss; GA 1.51 point D loss
Democratic Performance (NC compared to GA)
2004: NC +2.24
2008: NC +2.80
2012: NC +2.96
So, after hundreds of millions of Democratic dollars spent in NC in 2008, 2012 & 2014, NC has managed to widen the gap between it and GA by a mere 0.72 points.
Hundreds of millions of dollars, a Democratic convention and three rounds of on-the-ground grassroots and party efforts have yielded less than one point of progress when compared to Georgia over eight years, with virtually no net improvement between 2008 and 2012 between the two.
A good ground game can yield 2-3 points in an election cycle. I only can imagine what Georgia's numbers would have looked like in 2008 and 2012 had it been given the same attention...
One big problem going forward in NC is that - and this is of course my opinion - the Democratic share of the white vote still has room to fall further. Obama got 35% of the white vote in 2008 & 31% in 2012; Hagan 33% in 2014. If we're to believe exit polls, then Kerry received only 27% in 2004. In addition, NC blacks - according to exit polling - voted only 85% for John Kerry in 2004 (compared to 88% in 2004 in GA).
On the other hand, GA whites really can't go any lower than they already have. They were 23% for Kerry in 2004, 23% for Obama in 2008, 20% for Barnes in 2010, 20% for Obama in 2012 & 23% for Nunn/Carter in 2014. The rural whites in Georgia have by and large already defected; in NC, this is not as much the case, so there is more room for losses in this area.
I think when you consider that blacks seem to be slightly more Democratic in GA than NC, blacks are a greater share of the population in GA than in NC, whites' preferences for Ds in GA seem more stable than in NC, and that GA's non-white population is growing at a faster rate than NC, that GA may actually be the real/next Southern state to keep an eye on. 
