I agree that between 3 amd 3:30, depending on luck and how fast you are.
We flew in on 4/21 and I think deplaned between 3:40-3:45 (I was distracted). We went quickly to ME (dh was walking fast, I had to run to keep up!) and boarded almost immediately. Our bus pulled out of ORL at 4:05, we made one other stop on the way, and we went to Pop, checked in right away and were in our room at 5pm.
We stopped for nothing when we got off the plane. No bathroom trip or anything. You may not get as lucky with the bus being there so quickly and most people weren't booking it for ME like we were, lol.