The concern was raised by a Barclays analyst who said that "even a small percentage" of customers who took up Apple's $29 battery offer could translate into a "meaningful impact on iPhone sales".
The analyst reckoned 519 million iPhone owners, or 77 percent of iPhone users, are eligible for Apple's offer, and that about 52 million would take it up.
If 30 percent of those people don't buy a new iPhone in 2018, Apple could miss out on 16 million iPhone upgrades this year. Barclays expects that scenario could impact its 2018 iPhone revenue estimate by negative four percent.
Apple announced it would replace aging batteries for $29 instead of $79 on iPhone 6 and newer models after admitting it purposely slowed the performance of handsets to stop unexpected shutdowns on phones with worn batteries.
Though Apple said it would never intentionally shorten the life of an iPhone, the unexplained performance loss nevertheless gives consumers a strong incentive to upgrade.
Customers are angry that Apple didn't explain this loss of performance when it implemented the feature in iOS 10.2.1 early last year, in response to numerous iPhones mysteriously shutting despite the battery having a partial charge.
Only after being caught recently did Apple finally reveal that replacing an aged battery with a new one would restore an iPhone's performance to normal, enabling apps to launch faster and improving users' general experience.
Although consumers upgrade phones for numerous reasons, such as exclusive features in newer models, it is plausible that a sudden boost in performance on an older device would dampen the urgency to upgrade.