Enter QLACs. Of all the longevity annuity proponents, perhaps none is as influential as the U.S. Treasury Department, which issued guidance last year paving the way for QLACs in 401(k) plans.

Under the new rules, participants in 401(k) plans can move 25 percent of account assets, or a maximum of $125,000, into a longevity contract that distributes savings, typically beginning at age 80 or 85.

The assets invested in QLACs will not be subject to required minimum distributions imposed on 401(k) assets at age 70 ½ .

In issuing the guidance, regulators sanctioned what proponents of QLACs say is a necessary, proactive hedge against longevity risk.

READ: 6 things advisors should know about QLACs

The reality that many Americans can expect to outlive their retirement savings was crystalized last year when the Society of Actuaries released new mortality tables showing many baby boomers will live well into their 80s and beyond.

Still, data shows the average plan participant is vague on the value of annuity contracts in general, let alone their arguably more complicated QLAC-cousin.

The TIAA-CREF 2015 Lifetime Income Survey showed participants overwhelmingly value the option of guaranteed monthly income — 84 percent said so.

Yet only 31 percent said they are actively looking to convert retirement savings into guaranteed income, and almost half did not even know if the option to do so existed in their workplace plans.

Those figures don't even account for QLACs, which potentially face even greater participant ambivalence, given that the benefits to purchasing a contract are delayed, sometimes by 20 years or more.

Rafaloff acknowledges the challenge to educating participants on the value of QLACs.

READ: QLACs are changing Social Security timing game

She said the greatest tactical tool in that effort will come from sponsors themselves.

"For this to work, and we are seeing more people realize the value of longevity annuities, particularly in Washington D.C., you have to have a committed plan sponsor that wants to position their defined contribution plan as a retirement income plan. Without sponsors' desire to do so, the effort will fall short," said Rafaloff.

So far, sponsors have been receptive, she says, ever since Treasury released the new guidance last year, even going so far as to initiate communication by inquiring directly to MetLife about product availability.

READ: IRS verdict is in, buyer buyer jury out on QLACs

Yet other industry watchers have said regulators will have to reissue clearer annuity selection safe harbors for plan sponsors if wholesale adoption of QLACs, and other guaranteed income investments, are to reach full adoption.

Last fall, shortly after the Department of Labor rubber-stamped Treasury's new QLAC guidance, the Brookings Institution, a non-partisan think tank, published a paper in favor of longevity annuities in 401(k) plans.

The authors called on an improved regulatory framework. The DOL's existing annuity selection safe harbor places too much responsibility on sponsors in vetting an insurance company's capacity to meet long-term obligations, claimed the paper.

In 2008, the Department of Labor sought to clarify regulations for annuities in defined contribution plans, creating a safe harbor checklist that intended to protect sponsors from liability.

But the DOL took the effort too far, according to Brookings' research, creating more of a deterrent for sponsors than a safe harbor.

"It is widely believed that, for many employers, the analytical burden combined with the threat of legal action in the event of being accused of a violation is a sufficient disincentive to prevent them from offering an annuity option," concluded the Brookings paper.

For the past two years, the ERISA Advisory Council has recommended the DOL update its annuity selection safe harbor in order to encourage more lifetime income options in plan.

For their part, MetLife isn't waiting for the DOL.

Rafaloff explained that as of now, New York state insurance regulators have signed off on the QLAC line, as the company awaits authorization in all 50 states, which she expects to happen by the fall.

Until then, Rafaloff and her team are reaching out to sponsors throughout the country, hoping to not only advance the conversation on QLACs but to motivate a change in how sponsors and participants regard their 401(k) assets.

"Sponsors will be our main partners on QLACs. We've developed and continue to develop communication and education tools sponsors can customize and then pass on to their participants. Ultimately, adoption of QLACs will depend on sponsors' commitment to them," said Rafaloff.

As with most components of plan design, she expects large plans will move the market on QLACs, but she is quick to emphasize that small and midsize plans are also MetLife's prospects.

While Rafaloff did not discuss what participants are likely to pay in fees, or plan advisors are likely to make in commissions off QLACs, she did say the products will be priced consistently to participants, no matter the size of the plan they're enrolled in.

The $125,000 limit on 401(k) assets that can move to a QLAC is the perfect place for regulators to start, she said.

According to a MetLife fact sheet, a 65 year-old investing the limit would see a $1,878 monthly benefit begin to stream in at age 80, if he or she purchased a contract with a death benefit, which returns the premium in the event a participant dies before benefits begin. Without the death benefit, guaranteed monthly income goes up $2,488 a month, beginning at age 80.

"We think QLACs give participants the best option to assure they don't outlive their savings," said Rafaloff.

"For now, the goal is to get participants comfortable with converting assets," she added.