Can iPhones get old to the point where they can’t update

An iPhone 7 cannot update higher than the most recent “point” release of iOS 15. It will still get any critical security updates, but it can’t run iOS 16 or later.

Go to Settings/General/About and note the iPhone Model Name, then check its version compatibility from this list (note that this is current as of September 16; it will change when iOS 17 is released) :

• iPhone 8 or newer, including SE 2nd and 3rd editions, you can update to 16.6.1
• Any iPhone series 6S and 7, and original SE: You can update to 15.7.8
• iPhone 5S or 6: You cannot update to iOS 13 or higher; you can update only to iOS 12.5.7
• iPhone 5: You can update only to 10.3.4
• iPhone 5C: You can update only to 10.3.3
• iPhone 4S: You can update only to 9.3.6
• iPhone 4: You can update only to 7.1.2

If your phone is eligible to be updated go to Settings/General/Software Update and follow the instructions.

Pragmatically speaking once an iOS version is no longer supported on “new” phones, the 3rd party app developer support begins to taper-off.

Apple will continue to provide bug and security updates to iOS15 for quite some time. (one came out just this past week)

When to “upgrade” depends on your apps in-use, and your personal “needs” and “wants” but “most” users could probably continue using a “7” for another year or two; possibly even longer.

Yes. An iPhone 7 isn't capable of 16 or above, and all other models will eventually reach their limit if they haven't already.

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An IPhone 7 cannot be upgraded beyond 15.X.X.

If security issues are found, they will patch it with a newer version of 15, but it will not receive any new features.

It’s already here. But a lot of people want one, so it may be a month or more before you can get one.