Georgia Southern is a strong team for the Sun Belt. They don't have the depth to be a good FBS team yet, but I don't doubt they will. I could see GSU eventually joining a conference like the AAC. I don't see them ever breaking into the Power 5, but who knows. There are many, many things that will change over the next 10 years at GSU to make them more competitive with the big boys of the FBS.
However, I agree with mts315, the second half was an aberration, rather than the rule. A GT team came out in the second half and got punched in the mouth by a strong GSU team. That team has heart and some big time players. Unfortunately for GSU, there aren't enough big time players there yet. That may change, we'll see. But if GT doesn't turn it off at half-time, that game ends with a 56-24 score, or something like that. GT came out in the second half cold and GSU almost make them pay for it.
In the end, the more talented team usually wins. This doesn't happen every time, but mostly it does. After watching them beat App State, I think GSU will compete very well in the Sun Belt. Give them a few years of recruiting and improving facilities and I could see them moving up to a higher tier conference. If they play that game 20 times, GT will win 19 of them, if not 20. The talent/depth differential is too disparate right now.