While it's certain that Apple won't be vacating all of the commercial property they've occupied over the last few years, when their Campus 2 opens next year, some of those properties are sure to become surplus space and unnecessary expenses as far as the company is concerned. And while some of that space will be immediately snatched up by the growing collection of enterprises that participate in Apple's ecosystem or cater to their employees, there's still likely to be a spike in the commercial property vacancy rate.
Anticipating this, Cupertino and other nearby communities should be thinking about whether they want to allow those properties to sit idle, waiting for other suitable tenants to come along, or for Apple to again outgrow their own facilities, or should they perhaps encourage their conversion to other uses: housing, mixed use, indoor vegetable production, etc. This would be a good time to start examining and if necessary reforming their zoning ordinances, to clear away legal obstacles to alternative uses of what might otherwise become a problem.
Here's what a few communities are doing with abandoned shopping malls...