I'd say it depends. With what you wrote we don't have enough information. I can tell you from personal experience as someone essentially in the same boat as you, the following:
1) Of those that still get symptoms while on 80mg PPI, the vast majority don't have abnormal acid reflux. (It could be non-acid reflux, weakly acid reflux, etc., or not reflux at all). Remember, just because the acid is out of your reflux does not mean that you don't have GERD...you are refluxing all of the time, it is just that the acid is out of it.
2) Barrett's is generally found upon the first endoscopy. I have had GERD for 5 years and was told that "If you are afraid of esophageal cancer, don't be". It seems pretty sure that Barrett's always precedes esophageal cancer, and if you haven't developed Barrett's after 5 years, odds are you will never develop it. I was told that this is likely due to 'genetic factors'.
You would need additional testing, like motility and PH testing, to find out what is causing your pain.
Try reading something like the following. If you can't find it online, give me your email and I can send it to you.
Persistent Reflux Symptoms in the Proton Pump Inhibitor Era: The Changing Face of Gastroesophageal Reflux Disease
Fby Dellon, Evan S and Shaheen, Nicholas J