They will be wrong.
In fact, Phelps has stumbled along an uncertain road for the last 18 months as he tries to get himself on track for a fifth Olympics. His Sept. 30 drunk driving arrest and subsequent six-month suspension were just part of that story. He has also struggled with transferring his practice form into races.
If this tale ends with Phelps in his customary spot atop an Olympic medal stand, close observers will look back on the last few days in San Antonio as the dramatic turning point.
It wasn't just that Phelps, who grew up in Rodgers Forge and recently turned 30, won his first three events at Phillips 66 National Championships. He was expected to do so, with most of his top competition in Russia for FINA World Championships (Phelps missed that event as part of his punishment for the DUI).
It was that, for the first time since he came out of retirement in spring 2014, he seized his old perch as the best male swimmer in the world (Bethesda resident Katie Ledecky was somehow even more dominant on the female side, winning five world championships at distances ranging from 200 to 1,500 meters). In each of his likely Olympic events — the 200-meter butterfly, the 100 butterfly and the 200 individual medley — Phelps posted the best time in the world this year. He even managed a personal best in the 200-meter breaststroke, which he swam as a lark.
His longtime coach, Bob Bowman, said he has not swum so well since 2008, when he won a record eight gold medals at the Beijing Olympics. A "flashback to the good old days," Bowman said in a Monday text from San Antonio, where Phelps was about to finish his meet with the 200 breaststroke.
"I am very happy where I am right now," Phelps said after his victory in Sunday night's 200 IM. "This is a great foundation, a place where we've never really been in a long time leading up to an Olympics. I definitely wasn't like this leading up to '12, so it's probably been since 2007 that we've been like this."
Bowman cast Nationals as the meet where Phelps needed to translate hard work in practice to competitive excellence. He did more than that in a performance that "greatly exceeded" his coach's lofty expectations.
Phelps was so good that Bowman told reporters in San Antonio he had recalibrated his thoughts about the next year. He now believes Phelps can swim even faster than he did in 2008, when he and other top swimmers wore non-textile bodysuits that helped them smash records in virtually every event.
A personal best in one of his signature races would be nice, Phelps agreed. He hasn't pulled that off since 2009, though he won four gold medals at the 2012 London Olympics to increase his Olympic record to 18 golds and 22 overall medals.
Former Olympic gold medalist Mel Stewart, who covers the sport through his web site SwimSwam, made aggressive predictions about Phelps' performance in San Antonio, even taking some heat from readers for his optimism.
"He went even faster," Stewart said. " When people saw that 1:52 go up on the board for the 200 fly, there was a collective gasp on deck. It was like, 'Are you kidding me?' "
He came away believing Phelps really might set another world record or two before he's done.
The key, Bowman said, is for Phelps to continue pushing himself in training through the fall and winter as he prepares for Olympic trials next June. Autumn tends to be a time when elite swimmers relax. By his own admission, Phelps hasn't worked hard through that part of the calendar since 2007. His DUI last year came in the fall.
But as Phelps prepares to relocate to Tempe, Ariz., where Bowman will take over as head coach of Arizona State, he has promised there will be no let up.
Bowman has said the record-setting Olympian will compete as often as possible in hopes of remaining sharp. Possible winter stops include the Arena Pro Swim Series meets in Minneapolis, Nov. 12-14, and Austin, Texas, Jan. 15-17.
Phelps slapped the water in triumph Friday night after he won the 200 butterfly — a race he was in no shape to swim last year — in 1 minute, 52.94 seconds, his best time since 2009.
His reaction was about more than winning a national championship. He had allayed his own fears that he might never again be the world-conquering swimmer of old. A year of genuine hard work had brought him back to where he felt he belonged.
The dramatic centerpiece of Phelps' weekend was his victory in the 100 butterfly Saturday night.
The intrigue began earlier in the day on another continent, where South African Chad le Clos — the guy who upset Phelps in the 200 butterfly at the 2012 Olympics — won a world championship in the 100 butterfly in a blistering 50.56 seconds. Le Clos, never lacking for confidence, said Phelps could "keep quiet now" because he hadn't swum a better time in the race in four years.
That little love letter from Russia was the rough equivalent of waving raw hamburger at a tiger. Sure enough, Phelps ripped off a time of 50.45 seconds a few hours later in San Antonio.
"I welcome any comment someone wants to say," he said afterward. "I love it. I absolutely love it."
That bit of intercontinental back and forth sets up a tasty rivalry story for next summer's Olympics. But the mere fact Phelps could rise to the occasion in such fashion suggested how far he has come over the last 12 months.
At this time last year, he had little idea what his body would deliver on a given day. He might swim a near-vintage race in the morning only to blow a turn and lose in the evening. He knew he hadn't put in the necessary work to do better, and he was angry with himself.
Phelps created further doubt around his swimming future when he was arrested for drunk driving last September. But he seemed to emerge from that personal reckoning a re-determined athlete, one who'd submit himself to the kind of daily grind he'd avoided for years.
Practice did not produce immediate results, however, and this mystified a swimmer who'd always been able to summon brilliance when he pleased. After he failed to qualify for several "A" finals at a meet in Charlotte three months ago, Phelps admitted he was uncertain when the payoff would come. Perhaps he even wondered if it would at all.
He needn't wonder any longer.
The Phelps of the last few days finished races with power. He controlled his speed perfectly in morning preliminaries and peaked in the evening finals. He had struggled to do those things since coming out of retirement last year. But finally, he seemed fully in command of his form.
"I think I'm getting the hang of this again," he said.