U.S. dominance continues as Olympic swim meet winds down

Michael Phelps celebrates after winning gold in men's 100m butterfly Friday / CHRISTOPHE SIMON

(CBS News) LONDON -- The competition at the Summer Olympics begins a shift from water to land Saturday, from swimming and rowing to track and field.

For Team USA's swimming team, just as the old stars begin to set, the new ones begin to rise.

The swim meet is winding down and all the countries not called USA may be relieved.

It's been an American meet -- 28 medals compared to the next-highest total, China's, with nine. Four golds were up for grabs Friday night, and the U.S. took three of them.

Michael Phelps says this is his last Olympics, and he's going out in Phelpsian style.

The 100 meter butterfly was his second-to-last event. So why shouldn't it be another gold? It was -- his seventeenth - adding to his record 21 medals overall now. And he's got one more event -- a freestyle the U.S. is expected to win.

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U.S. swimming success seems secure in the hands of the upcoming generation.

Seventeen-year-old Missy Franklin took another gold in the 200 meter backstroke, her third. Her dominance in the pool is now an established fact.

But the Olympics create new facts all the time.

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When 15-year-old Katie Ledecky made the team, it was considered a surprise. When she simply swam away from the rest of the field in the 800 meter freestyle, it was a revelation.

How's the future of the U.S. Olympic swim team shaping up as Michael Phelps "retires"? "CBS This Morning: Satuday" co-hosts Terrell Brown and Rebecca Jarvis asked Time magazine Senior Writer Sean Gregory, who's covering the Games in London. To see the interview, click on the video at left:

"Yeah, it was really neat to swim right after Missy and Michael," she said. "Their wins pumped me up, and when I walked out of the ready room, Michael gave me a high five and wished me good luck, and that meant a lot to me."

And so the main stage now shifts from poolside to trackside.

Sanya Richards Ross won her heat in the 400 meter.

And Tirunesh Dibaba, from Ethiopia -- where else -- won her second straight gold in the women's 10,000 meters. And she barely seemed to be breathing hard.