By Joanna Stern

In this world nothing can be said to be certain, except Apple's willingness to sell you an iPhone, iPad or iWhatever, no matter the hour or season.

Benjamin Franklin penned that. After quickly erasing "death and taxes." On his iPad.

The observation has held up over the ages, and there's no better time to be wary of it than at this particular moment, which I'm calling The Worst Time to Buy Apple Products.

Regular readers of my column are familiar with my annual iPhone No-Buy Rule(TM). Once June rolls around, it's time to wait for the new iPhones, typically announced in early September -- though possibly later this year, given Covid-19-related delays. An Apple spokeswoman declined to comment.

What has changed is that, in 2020, more Apple hardware products fall into this no-buy zone -- and not only because of that once-in-a-lifetime pandemic we're living through.

On Monday, Apple announced new operating systems coming this fall to the iPhone, iPad, Apple Watch, Apple TV and Mac. Each of them promise to breathe new features into your current devices, enough that you might not even want to buy new ones. Plus, specific software features tease the likely hardware upgrades to come.

Heck, in the case of the Mac, it's not just a tease. Apple shook the foundation of its longstanding desktop and laptop computer platform by promising an Apple-silicon-powered Mac by the end of the year. Think of the software power of a MacBook, combined with the snappiness, battery life -- and apps! -- of an iPad.

So even if you saved big by canceling that family summer trip to Walley World and have some extra cash burning a hole in your pocket, put down the credit card and consult my Apple product do/do not buy list.

iPhone

Buy a new iPhone now? Nope, no, absolutely not. (Well, not unless you've been wanting the smaller, home-button-equipped iPhone SE.) I'm so confident in my do-not-buy-rule I'm ready to argue the case before the Supreme Court.

Even if you're the slightest bit tempted to get an iPhone 11 model right now, consider that new models (presumably the iPhone 12) are expected with new designs, better cameras and fast 5G wireless connectivity. If history repeats itself, they'll be priced the same as the current models. Also, consider that Apple has previously dropped the price on popular older models in September. My 2018 battery-life winner, the iPhone XR, dropped from $749 to $599 last fall.

Plus, the free iOS 14 update due in less than three months will come to all iPhones that currently run iOS (iPhone 6S and later). It finally allows you to decorate your home screen with widgets and group all your apps by category so you don't have to create folders. There are also a host of important messaging and privacy features. That might be enough to make your current iPhone feel fresh and new.

AirPods

Need some tiny white sticks for your ears? Go right ahead. In fact, the $249 AirPods Pro and regular $159 AirPods are only going to get better in the fall. Apple revealed this week just how much it can unlock in these tiny wearables with software.

With iOS 14, AirPods will now learn from your charging habits to optimize charging and reduce battery aging. AirPods Pro get an extra trick: a surround-sound effect that renders movie-theater audio that stays centered, even as you move your head.

There are reports that Apple is also readying over-the-ear headphones. It's something to keep in mind if you're debating replacing your over-the-ear Bose or Sony pair with AirPods. There are some reports of $159 AirPods coming in different colors, but that's not enough for me to tell you to hold off.

Apple Watch

I recently bought my father an Apple Watch Series 5 for Father's Day. We now need to talk about returning it. While I have strongly recommended the Series 5 (and Series 4 before that), I'm convinced the next watch will take another leap ahead in sensors. My tip off? Apple didn't talk much this week about new health features for WatchOS.

There are reports, for instance, that the wearable could, like a pulse oximeter, measure blood-oxygen levels, which among other things are tracked for possible indication of Covid-19.

Plus, the Series 5 really was the equivalent of an iPhone "S" year -- an incremental hardware improvement over the Series 4. It basically just got an always-on display and a compass. I'm betting we'll see a significant Apple Watch upgrade in the fall, with a drop in price for the current top models.

Plus, those older models will get WatchOS 7, which includes sleep tracking and new face customization.

iPad

If your old iPad is dying and you need something for Junior to watch "Zootopia" on for the 5,000th time during the family road trip, get a $329 iPad-iPad, (actually known as "iPad seventh generation" or "iPad 10.2-inch"). That and the $499 iPad Air were both refreshed in 2019 with support for the Apple Pencil and Smart Keyboard. The iPad Air has a better processor and slightly better screen, but I can't say if that's worth $170 to you. Both could be updated again before the end of 2020, but at this point an iPad is an iPad. Even an old one can work great.

The harder question comes with the new iPad Pros, refreshed in April. Before this week's Mac announcement, I would've said, "Sure, get one!"

The new $799 11-inch and $999 12.9-inch Pros, which I've been testing for a few months, are the closest thing to a perfect tablet/laptop combo from Apple. The new $299 Magic Keyboard is great to type on (though it is chunky), the trackpad works smoothly with the new cursor support and iOS 13 -- excuse me, iPadOS 13 -- finally has just about the right amount of multitasking and file management to really let me drive some work forward. Plus, the $99 Apple Pencil is smooth and getting new tricks with the fall software update.

If you are very much into drawing, or just like touching a screen to get around a computer, then yes, this is likely Apple's stylus/touch-screen computer for the time being. But now, as early as this fall, the coming Macs could marry what's best of the iPad Pros with what's best of MacBooks.

Mac

This is the toughest one, for reasons I've foreshadowed. Apple spent the spring releasing MacBook update after update, ending my longtime crusade to kill the atrocious butterfly keyboard. The current MacBook Pro and MacBook Air models have glorious new keyboards and improved Intel processors.

And yet, all I hear in my head is Tim Cook's words from this week's announcement: Macs will be moving from Intel chips to Apple chips starting this year.

What exactly happens when you stick an iPad Pro-like processor into a MacBook running MacOS? Will it provide the same power as Intel-based systems? MacOS Big Sur, coming this fall, will bring a lot of the styling of iOS and iPadOS. But will the new Macs ever support touchscreens? How about cellular connectivity? And how much will it all cost?

The sure bet is on improved battery life, better overall performance of Apple software, more seamless integration with other Apple devices and yes, iOS apps galore. I'm hoping for a snappy, super-slim laptop with iPad-like battery life and webcams.

If you need MacBook Pro power at this point, the higher-end machines are a safe bet. It will likely take a few years for the performance and app support to come. If you specifically need to run Windows on a Mac laptop, you'll probably need to stick to Intel chips for now. Keep in mind, though, that like Apple's transition from PowerPC to Intel, at some point the company will cease supporting Intel-based systems both with operating system updates and service and parts support.

If you're looking for the best portable laptop for under $1,000, the new MacBook Air is also safe. (You can even get a refurbished model for around $850.) It's a great choice for students heading back to school in the fall, and I don't think Apple's next big thing will come cheap.

Need an iMac? Hold off: The current one, a bit long in the tooth, is overdue for a redesign.

And if you're thinking that any MacBook you'd purchase right now comes with meaningful trade-offs -- of price, of battery life, of bulk -- it's worth waiting until the end of the year to see how these first Apple-powered machines turn out.

Don't worry, no matter how long you hold out, there's always that certainty: Apple will always have something to sell you.

Write to Joanna Stern at joanna.stern@wsj.com