Corporate defined benefit pensions may be coming off the endangered species list.

Not that traditional lifetime pensions will once again be the nation’s predominant type of corporate retirement program; no one predicts that.

But a new survey from the New York-based consulting firm Towers Watson shows clear signs that traditional pensions have lost as much ground as they’re going to lose and are now at a stable plateau. Of the employers that still enroll new hires in some sort of defined benefit plan – admittedly, a minority of the respondents — 68 percent said they had “made a formal decision” to keep offering the plan for the next two to three years.

Athough two or three years may not seem much of a commitment, Mike Archer, a senior retirement consultant in Towers Watson’s Parsippany, N.J. office, points out that the plans have already survived two recessions in the past decade, as well as the general trend away from pensions. “If these companies haven’t closed or frozen them after all that, and if the companies don’t change them in the next three years, I don’t know what it would take to change them,” he says.

Arthur Noonan, a senior partner at another consulting firm, Mercer, is more pessimistic in the short run but more optimistic over the long. For the short term, he cites a survey of some 200 companies that Mercer co-sponsored last fall, in which around one-fifth of the respondents said “they were still looking at whether or not to freeze or amend their plan.” Over the next three to five years, however, he continues, not only will companies stop freezing, but some will even restore lost pension plans.

“It takes a while for the change to occur,” he says. But eventually, “employers are going to have to say, ‘If defined contributions doesn’t work, I need enough defined benefit features that I can achieve what defined benefit plans were providing me in the past – a reason for employees to stay, and a message about when the time to leave should be.”

Today fewer than 31 percent of public- and private-sector workers today rely on traditional pensions as their main source of retirement income, down from nearly 57 percent in 1988, according to the Employee Benefit Research Institute. In the Towers Watson survey, only about one-third of the 424 large and midsize companies polled last fall were enrolling new hires in such plans.