Challenger's concern is that, with so many employers so dependent upon older workers, very few seemed to be planning around a possible mass exodus, or brain drain, from this group.

"While survey after survey indicates that more Americans plan to continue working well into their retirement years, employers counting on that may still find themselves shorthanded if they fail to gauge potential retirement activity in their own organization," Challenger Gray said in a release.

Its CEO, John A. Challenger, was more explicit.

"Simply because more workers expect to remain employed beyond the traditional retirement age of 65 does not mean they will. Nor does it mean that they will stay with their current employer," he said. "With the leading edge of the baby boomer generation reaching age 68 in 2014, it is critical that companies understand their exposure to brain drain related to retirement."

The survey revealed what could be a critical lack of tracking the plans of aging employees. For instance, it found:

• 59 percent of employers rely on department managers to stay informed about their staff's potential retirement plans, yet most have no formal way of measuring that.
• Only about 6 percent use employee surveys to gauge possible retirement activity.
• 30 percent don't take any steps to anticipate retirement activity, instead learning about retirements only when employees initiate the process.
• More than half of respondents said their companies are "very concerned" or "somewhat concerned" with the coming retirement surge due to the fact that those planning to leave are in key, hard-to-fill positions.

 "Small to medium-size companies will probably feel the biggest impact of any retirement surge that comes to pass" Challenger said. "Their size means that they are less likely to have a deep pipeline of talent to feed into the positions left by retirees. These companies may need to do more to retain their most experienced talent.

"Instead of letting these workers leave for less-demanding job opportunities, for example, employers may want to find a way to cut the individuals hours and responsibilities. The person may be willing to accept lower pay and benefits in exchange for more flexibility to travel, volunteer or enrich their lives in other ways. Meanwhile, the company can continue to benefit from the continued employment of someone who can mentor younger employees and ensure the succession of specific corporate knowledge from one generation to the next," said Challenger.