In its June 2011 Project Update, FASB indicated that it wanted to issue a final standard in 2011. However, if the new standard has changed significantly from the Exposure Draft issued last August, it may be necessary to issue a new exposure draft and extend another comment period. "It's a guessing game," Davis says.

Even so, CFOs should start preparing now to collect information, such as the terms and rates on the leases within their portfolios, so that they'll be ready to do the calculations, says Jones Lang LaSalle's Mumaw. Depending on the size of a company's portfolio, that may take a year, she says. It also makes sense to develop or acquire technology that can house the lease information. They'll also need to decide how to handle other contracts that might be impacted, such as loan agreements that limit the amount of debt on a company's balance sheet.

While the changes are significant, they are unlikely to lead to a massive shift from leasing to buying assets, says Brian Radecki, chief financial officer with CoStar Group, a Washington, D.C.-based provider of commercial real estate information

"You try not to let the accounting dictate operationally what the business does," he says. The proposed rules make up just one factor that a firm will look at when making a lease-versus-buy decision, Radecki adds. Companies also will consider their estimated rate of return, and their ability to make the purchase in the first place.