In 1981, the Internal Revenue Service published regulations authorizing 401(k)s, the first participant-directed retirement plans in the U.S. Six years later, about 15 million Americans were actively participating in 401(k)s.

At that time, few people would have believed a prediction such as this: Over the next two decades, participant-directed plans will grow to cover 60 million U.S. workers, hold over $3 trillion in assets, and dominate the U.S. retirement plan market. Yet, this has happened.

Here is a prediction for the next 20 years: Participant-directed plans, as we know them today, will become dinosaurs. By 2027, perhaps 100 million U.S. workers will participate in workplace retirement accounts that resemble today's self-directed IRAs. These accounts will let workers choose their own investments from a vast array of stocks, bonds, mutual funds and ETFs. Each participant will be able to control personal plan costs and decide whether and how to receive objective financial advice from a qualified professional.