If you mean the wait in the actual FoP line, it took us about 10/15 min. to get into the loading area (before the pre-shows) once they let people into Pandora. You show up for rope drop around an hour early, and then they open the park a bit early (usually), and then the herd gets stopped at Pandora entry, then led to FoP and arranged in a line through the FP queue of FoP. This line can appear longer than it is because they are winding people through the FP line and loading the theaters. This was my experience the week of July 5th.
It's hard to get a genreal exact time because they open the park earlier than advertised and then hold the herd at Pandora, then line everyone up once the herd gets to FoP. But, we rode FoP, then River Journey, and were done by a little after 9 (it was an 8am EMH morning). I don't know if regular non-EMH mornings would be significantly different.