FYI - we were 5 in the lounge in late August, parties of 3 and 2. Three of us were small eight year olds, so we told the person checking us in we'd be fine sharing the 4-top among five. She said it was a fire code thing and that they absolutely couldn't put a 5th person at a 4.
When we were being seated (4- and 2-top right next to each other) our server came over and asked the CM seating us, "Why are you splitting them up? We can't find somewhere together?" I chimed in that they were lounge reservations and we'd been told we couldn't do more than four at a table. He said I was absolutely correct, he was sorry, but he couldn't seat 5 together for the lounge menu.
So, I would call that pretty definitive evidence that they will not seat above 4 in the lounge, there's no way to eek in one more person.
ETA They also wouldn't let us check in a moment early. I had 6:30 and 6:35 and the CM at the front door had me stand to the side until the clock for Mission Space hit exactly 6:35. So, I wouldn't try going early to get the 3 party seated early.