"It's interesting how we have a handful of really important systems that have held on," he said. "The mainframe tends to be the one we all point to but I'm sure there's others out there. We hear about applications that still run on what we call legacy from our standpoint, like an old Windows NT server or an old 1995 machine."
While these companies are wed to legacy systems, they don't want to deal with the economic and labor issues tied to maintaining older technologies. Instead, they'll outsource upkeep to consultants, who may land lucrative contracts if there is enough market demand for their skills.
"It's probably going to be cost prohibitive or just so hard to find that one guy that knows that technology who's willing to work on one or two legacy systems," Engates said."Your demand goes way up if you're a consultant that's managing hundreds of mainframes. They're still out there."
At companies that have modernized their systems as technology evolved, retirement may not be as much of an issue since employees learned new skills when the IT changed, avoiding the challenge of transferring knowledge between staffers.
"You need to be proactive on optimizing your ecosystem," said Verizon Enterprise Solutions CIO Ajay Waghray. "And that forces the retirement of multiple processes and systems that tend to have created that long living complexity that creates all the challenges."
Last year Waghray retired approximately 160 systems and has so far retired 60 in 2103.
"Even before this whole cloud orientation became a buzz we were already applying those techniques to stay lean and agile," he said.
Verizon is also proactive in maintaining "a pretty good [employee] progression map, particularly in managerial roles," helping the company plan for future employment needs, some of which maybe caused by retirement, Waghray said.
"We tend to know if we have a certain group of people that we have a need for, be it retiring or otherwise," he said.
To fill employment needs, Verizon uses mentoring programs, college recruiting, telecommuting, job sharing and part-time positions.
As for the possibility of retired employees returning as consultants, the demand isn't there now at Verizon.
"I haven't really heard the need to say will you come back," Waghray said. "We might have that in the future but we've not seen that."
At Intel, which is in the early stages of exploring the impact of employee retirements, flexibility extends to helping workers take positions outside the company at nonprofits.
Last year the chip maker launched the Intel Encore Career Fellowship, a pilot program that gives near-retirement employees a $25,000 stipend and allows them to spend one year applying their skills to new positions with social value. The program is part of a greater effort by nonprofit Encore.org that aims to help retirees use their skills in second careers with social purpose.
"We don't have the need yet to say with enormous numbers departing how do we retain some skills, how do we retain some of the institutional knowledge," said Julie Wirt, the company's global retirement design manager. "We're just starting now to sit down and think about how we're going to approach that. In five years we'll be in a different situation."
As employees near retirement they question whether to update their skills or consider other ways to use their IT backgrounds.
"At a certain point they say 'It's probably time for me to reskill again. Do I want to do that or do I want to think about something new as I'm kind of on the brink of retirement,'" said Wirt.