The photo is of the east course.
I have read that the USGA believes it can fit 20,000 on the course. I believe the property is about 125 total acres.
I suppose with some imaginative grandstand locations, for instance, perhaps the lawns of the houses along the 14th and 15th holes, or the abutting road could be used, 20,000 could somehow attend, but I really wonder how much you will be able to move around. This course is superbly routed onto this site, but accomodating spectators was not part of the equation. Crossovers will be a challenge because there isn't much space to crossover into in many locations. Holes like 7, 8, 14, and 15, have limited room on one side and no room, or charitably, even less room, on the other side of the fairway. That's true even after skinnying the fairways down to 20-25 yards wide.
I expect it will be a competitive competition that I will be very happy to watch on my couch. If they are using the lawns or abutting roads to accomodate spectators, that will help, but I believe corporate tenting is going onto many of those areas.