I'm surprised it's only 4 stories. I would of added 3 more stories and added capacity for several more thousand employees. I can easily see them out growing the space very quickly in the next 20 years and possibly building two other circles in the empty spaces beside the circle.
Well it's either that, and having a high likelihood of spreading the company around 30 crappy buildings all around Cupertino again, or using the large fields as building spaces for new circles.
