Retirement bottom line: Many will have to work until 70

— -- Will the old thirtysomething gang still be showing up for work at seventysomething?

That could be the case if they hope to enjoy a financially secure retirement.

Baby Boomers, with their inheritances, homes, and old-fashioned pensions, may appear to be on track for a solid retirement — but some experts say the forecast for the generation born from 1946 through 1964 isn't necessarily so rosy.

While Boomers are more likely than younger workers to have defined-benefit pension plans and certain other advantages — that's particularly true of older Boomers — many may wind up financially ill-prepared for retirement unless they work longer and save more.

The recent financial crisis took a toll on wealth; inheritances on average won't be that big; traditional pension benefits are phasing out; and many shop-till-you-drop Baby Boomers simply haven't saved enough money to last through retirements that should stretch beyond those of previous generations, economists say.

"The majority of today's retirees are able to afford a decent retirement. However, this group is living in a "golden age" that will fade as Baby Boomers and Generation Xers reach traditional retirement ages in the coming decades," according to an October 2009 report led by Alicia Munnell, director of the Center for Retirement Research at Boston College.

"This gloomy forecast is due to the changing retirement income landscape. Baby Boomers and Generation Xers will be retiring in a substantially different environment than their parents did," the report notes, citing longer life spans and retirements and declining "replacement rates" — retirement income as a percentage of pre-retirement income.

As of 2009, in the wake of the housing and stock market crises, some 51% of households were at risk of being unable to maintain their pre-retirement standard of living at age 65, the authors calculated in their report, "The National Retirement Risk Index: After the Crash." Some 41% of early Boomers, 48% of late Boomers and 56% of Gen Xers were at risk, they said.

The financial crisis, however, can't be blamed for everything.

"They weren't prepared even before the crisis," Munnell told CNBC recently. The report noted that two years earlier, 37% of early Boomer and 43% of late Boomer households were at risk.

"The gist of this whole story is that retirement ages are increasing as people live longer and health care costs rise, and at the same time the retirement system is retracting," says Munnell.

Eligibility for full Social Security Insurance benefits is gradually rising from age 65 to 67, Medicare premiums will account for a bigger chunk of spending, increasing numbers of households will be taxed on their benefits, "and people really don't save on their own," says Munnell.

Some researchers believe most Baby Boomers are indeed wealthy enough to maintain their pre-retirement consumption, says David Wise, an economist at Harvard's Kennedy School of Government. Wise, however, says it's instructive to look at the real financial status of elderly retirees near the end of life.

"When you look at it that way, it doesn't look as favorable," he says.

In a recent study, Wise and two colleagues found that "a substantial fraction of persons die with virtually no financial assets - 46.1% with less than $10,000 - and many of these households also have no housing wealth and rely almost entirely on Social Security benefits for support."

Based on a replacement rate measure, "many of these households may be deemed to have been well-prepared for retirement, in the sense that their income in their final years was not substantially lower than their income in their late 50s or early 60s," the study notes. "Yet with such low asset levels, they would have little capacity to pay for unanticipated needs such as health expenses or other financial shocks or to pay for entertainment, travel, or other activities. This raises a question of whether the replacement ratio is a sufficient statistic for the 'adequacy' of retirement preparation."

Given these findings, expectations of a life-saving wealth transfer to the Baby Boomers may be overblown. Maybe half the Baby Boomer population will inherit money from parents, with a median amount of $40,000, according to Boston College's Munnell.

"It's not going to be enough," she says.

People increasingly will rely on their 401(k) retirement plans, but the savings rate isn't reassuring.

According to BC's Center for Retirement Research, 62% of workers were covered only by traditional defined-benefit pension plans in 1983, compared with 17% in 2007. Those covered exclusively by 401(k) plans increased to 63% from 12% during the period.

"In theory 401(k) plans could provide adequate retirement income, but many individuals make mistakes at nearly every step along the way," the center's report states, citing research showing that the median 401(k) and IRA balance for those near retirement was $78,000.

Annamaria Lusardi, economics professor at the George Washington University School of Business, points to a general lack of financial literacy and planning.

"A sizable group of the population has not even thought about retirement, so there are a lot of people that are approaching retirement without any preparation for it," she says.

She also says retirement planning can be a "sophisticated calculation" that chief financial officers with MBAs handled for traditional pension plans. Now many workers must decide how to invest their own retirement wealth in 401(k)s and IRAs, as other major financial forces —spending on children's college education, accumulation of credit card debt — take a toll on retirement savings.

The challenge may also be compounded by the boom-bust cycle of the housing market. Many people took money out of their homes through refinancing, lowering their equity stake. Even for those who did not do so, the subsequent housing price slump has eroded equity, taking a bite out of what's been a traditional retirement resource.

"I think it's very important that we provide ways to help workers make good decisions about retirement," says Lusardi, suggesting that employers provide financial education.

Not every economist sees a bleak future for Boomers, and even those with significant concerns see ways to make those retirements brighter.

"It's basically a very mixed bag. Richer Baby Boomers will do better than previous generations," while the poor will do worse as pensions disappear for many workers, Massachusetts Institute of Technology economics professor Jonathan Gruber said. The extremes in income distribution seen during the working years persist in retirement, with the wealthy in each generation doing better and children of the rich becoming rich themselves, he says.

The amount of income needed in retirement is a subject of disagreement. While the Department of Labor and financial planners recommend an 80% replacement rate, some consider that too high.

An Urban Institute report this year called the 80% rule of thumb "misguided," stating that Americans aren't necessarily saving too little, but they need to save enough so that spending doesn't have to drop sharply in retirement.

Economist John Turner, director of the Pension Policy Center in Washington, D.C., thinks retirees above the poverty level should do OK with at least 60% of pre-retirement income, and suggests that saving 10% of earnings for retirement is enough. But that's more than most people are saving, he notes.

"The way out of this box is to work longer," says Boston College's Munnell. "Now that's harder in this environment where we have high levels of unemployment, but that's really in the end what's going to keep people financially sound. If people work until age 70, I think the vast majority of people would be perfectly fine in retirement."

Copyright 2012 CNBC.com.