In our Games Room we have a 75 inch 4K Samsung connected to our Dolby Atmos System (7.2.4). When we bought it my wife tapped out at that size, while I was ready to pull the trigger on an 85. (Which was big only a few years ago!) I've always thought bigger is better way back to 37 inch CRT days. (She sent me out for a 29 inch Sony and I came home with that monster. I think that's why she came with me shopping for the 4K TV.)
However, front center channel speaker placement would be a concern over about 85 inches for me. We went to the QLED Samsung over a projector primarily as we like to have the sun come in the room at times, and wanted a "bright" picture, I was concerned with that. I definitely think these larger screen LEDs are going to cut into Projector sales.