CHICAGO—McDonald's imminent decision to leave Oak Brook for downtown Chicago has many observers wondering what could fill such a big hole in the market, and whether that vacancy will imperil other development plans.

But Jim McDonald, vice president of development for Ryan Companies US, Inc., which has an ambitious vision for Oak Brook, tells GlobeSt.com that a lot of users won't find the 1980s-era campus very enticing. In fact, since so much suburban office product was built decades ago, there is a robust demand for customized spaces that provide the open-floor plans and amenities that tenants now consider essential.

“It could be a good mixed-use destination,” he says of the sprawling, low-rise McDonald's campus. And although it is possible that some large tenant will find the bucolic setting attractive and agree to occupy the property, “that market is somewhat limited. Buildings of that size and age are becoming obsolete in the new office market.”