That money would not be subject to required minimum distributions at age 70 ½, as 401(k) assets otherwise are. Instead, assets in QLACs will be distributed by no later than age 85, guaranteeing income later in retirement and helping assure 401(k) participants don't outlive their savings.

Also read: How to make DIAs work in retirement plans

The question of how readily QLACs would be adopted has been top-of-mind for the industry since Treasury's announcement.

"The goal to help individuals maintain an income stream throughout the golden years is laudable," Mark Weisberg and Linda Lemel Hoseman, partners with the Chicago-based law firm Thompson Coburn, wrote in a blog last year. But the guidance issued by Treasury contains "numerous requirements and possible traps" that may slow sponsors' adoption and participants' understanding of the products.   

And that may, in fact, explain why providers aren't flooding the market. 

In September, soon after the DOL signed off on Treasury's initial guidance, Ross Goldstein, managing director of retail annuities with New York Life, suggested the firm might be willing to enter the market. 

At the time, New York Life was "digesting the specifics of the regulations," Goldstein said. 

But on Tuesday, a company spokesman confirmed New York Life wasn't looking to build a product for 401(k) distribution. 

That is in spite of the company's notable success selling deferred income annuities in the retail market. 

In October, New York Life announced its Guaranteed Future Income, a DIA product sold to individuals, had generated $2 billion in premiums since its rollout in July 2011. The insurer claimed 10 other carries had subsequently issued new DIA products as a result of its success. 

Indeed, in 2011, data from LIMRA and the Insured Retirement Institute showed DIA sales at $211 million. By 2013, the figure had catapulted to $2.2 billion. LIMRA expects 2014 figures to hit $2.8 billion after they are ultimately tallied. 

Also read: IRS verdict is in, buyer jury out on QLACs

A spokesman for Prudential also said the company has not developed QLACs for the 401(k) market. It might at some point, but Pru wasn't saying either way.   

The first insurer to throw its hat in the ring after regulators green-lighted QLACs was American General Life Insurance Co. Its product, however, is aimed at IRA holders only.

The Principal Financial Group followed soon after, also with a QLAC option for retirement savers holding traditional IRA accounts. A company spokesperson, however, said no option has been designed for 401(k) participants. 

MetLife, meanwhile, has said it planned to offer QLACs to its DC retirement plan customers. 

That was last year, after Treasury issued its guidance. In an email Tuesday, Roberta Rafaloff, vice president of the firm's Institutional Income Annuities unit, said MetLife has yet to enter the market. "But we hope to be soon," she said.

Correction: Based on erroneous information provided by a Prudential spokesman, an earlier version of this story incorrectly said the company had decided not to offer QLACs in group retirement plans.