My sense of it (your mileage may vary) is that there has been a permanent change brought about by Covid. People are reconsidering their work-life balances, driven by the wake-up call that things entirely outside your control can shorten your life expectancy dramatically. A "don't plan for retirement, do it now" sort of thing.
Combine that with another Covid-driven thing wherein people don't want to vacation in large, crowded environments anymore. Resorts are out, AirBnBs are in. I don't see this changing, though resorts will still have customers, because more people are traveling.
All of this is to say that boating is more popular because of Covid, and I think that popularity is here to stay.
As the joke goes about predicting the future, the only guarantee is that you'll be wrong. Or you might be right, but without being able to predict when. In other words, no one really knows.
What is guaranteed is that the SARS-CoV-2 virus is going to be with us for the foreseeable future. Probably beyond the remaining lifespan of most of the people on this forum (certainly myself). There will be no 'end' to this pandemic.
What is mostly unknown and unpredictable is how people will react. At least here in the U.S., the country and people initially went through a shock stage, with precautionary measures effected by governments. The surge in interest in boating was one of the results, with people looking for 'safe', 'socially distanced' activities they could do while reducing the risk of getting infected.
Now my sense is that most people in this country are in a denial and delusion phase. In most areas I see very few people wearing masks (excepting Vermont and coastal Maine). People have decided they're "done with COVID", even though the virus is FAR from done with us. In short, few people care anymore. As a society, we've normalized and accepted horrifically high death and infection rates as a price we're willing to pay in exchange for being able to eat indoors in restaurants unfettered, and freedom from the tyranny of having to wear a mask while shopping.
All of which is reflected in the extraordinarily (and unnecessarily) high both total infection and death rates in the U.S. As a culture, we've effectively decided we'd literally rather have death than perceived impositions on our 'freedoms' (as long as those deaths happen to someone else).
Purely from the perspective of boating, it will be interesting to see how this plays out. On one hand, you may be right and most of the people who bought boats will stick with it.
On the other hand, I can see a few reasons why the boat market might change.
First, think of how many people try boating, and are turned off by the realities of maintenance, costs, and other headaches (that we accept as the price to be paid for boating). I've heard several newbies to the hobby complaining that they didn't realize it was so hard and expensive to keep a boat (and I've seen the result with their poorly maintained, poor condition misused and abused boats being offered for sale). More newbies might come to that same conclusion. Especially because...
Second, more and more people are returning to living as they did pre-pandemic, because they're 'done with COVID.' They're returning to their pre-pandemic hobbies, interests, and activities, travel, etc. They may not 'need' a boat as much any longer.
Third, there is widespread and growing consensus that the economy is going into a recession sometime later this year. The stock market is down about 20%-ish from its highs, technically putting it into a bear market (whatever that really means).
One of the biggest motivators of human behavior is FOMO - Fear Of Missing Out. It's been a sellers market for boats and prices have climbed to insane levels (even for poor condition abused boats from newbies) because buyers didn't want to miss out on getting a boat. Some sellers seem to have held out listing their boats, hoping for an even greater windfall. It might continue this way for a while. But if the tide starts turning the other way, whether catalyzed by an economic recession, or simply an increase in supply of people getting out, then FOMO could work the other way. If prices start softening, it could start a rush of boats coming onto the market out of fear for missing the peak and not wanting prices to go even lower before selling.
Ultimately, the only guarantee about the future is that it will arrive. Those that are around will see what happens. Until then, anyone's guess is as good as anyone elses.