But what's next for these individuals, many of whom face an identity crisis when they think about retirement? Are they senior citizens? Elderly? They don't feel that way. Neither young nor old, they are finished with midlife, yet they can look out to the likelihood of decades of vitality before becoming truly old. What might they rightly aspire to in the next phase? How will they define success?

While much about the goals and purpose of this period of life remains up for grabs, a central, defining feature is emerging. It is work. The vast majority of the Boomers are planning to continue working—full-time, part-time– in their so-called retirement years. Already we're witnessing an increase in retirement age—along with inklings of a new vision of work.

Consider a recent ad campaign from Home Depot and AARP announcing a new partnership to recruit older workers for the home renovation giant. Targeting men (and perhaps some women) who couldn't wait to get home from their midlife work to get to the tool shed, the campaign beckons them to trade in retirement for a new vision of what work can be. The banner: "Passion Never Retires."

Fidelity offers its own take. In a series of ads the financial services company features an aging boomer in front of a classroom, graying temples, full of engagement. The message at the top: "What did you want to do before you started doing what you're doing?"