Apple's software support is unmatched in the smartphone space, but it's still disappointing when your beloved iPhone does eventually fall out of favor with a new release of iOS.
If you are one of those users sporting an iPhone X, iPhone 8 or older who won't be able to download iOS 17 when it launches, don't despair. Your phone will continue to work as intended for the time being, with incompatibility unlikely to rear its head in terms of native Apple experiences or third-party apps; at least not for a while yet.
The more pressing concern is security, and even if your phone can't run the latest and greatest build of iOS, Apple still doles out security patches to iPhones running older versions. Apple makes a clear distinction on 'upgrades' versus 'updates' and, while the length of update support is far less concrete, iPhones not running on the latest version of iOS should still receive security updates for a few years after they fall off the iOS upgrade path.
That said, you should still consider that at this stage the security of your iPhone will continue to diminish, and once the updates also cease, you should seriously consider upgrading to a newer device that's still receiving security patches, at a minimum.
In fact, if that's where you find yourself as you read this, why not check out our best iPhone deals – both the iPhone SE (2020) and iPhone SE (2022) will be making the jump to iOS 17 later this year, and are the most affordable iPhones out there.