Regardless of any potential delays, shortages or other impediments, Apple’s upcoming next-generation iPhone models will fly off the shelves following launch. This is a given. As Apple’s announcement approaches and Apple fans get ready to upgrade, however, some may be in store for a rude awakening. Current iPhone users looking to part ways with an old model in favor of a shiny new handset have likely already missed the boat if they were hoping to sell their iPhones to help recoup money spent on a new iPhone. Read on for more.

According to data collected and analyzed by consumer electronics recycler NextWorth, the value of previous-generation iPhone models has historically declined rapidly beginning well ahead of next-generation announcements.

The average selling price of Apple’s iPhone 3GS and iPhone 3G models sold on eBay last year began to decline rapidly in mid-May according to the data, dropping between 10% and 15% by the time Apple announced the iPhone 4 on June 7th. The mere anticipation of a next-generation model is enough to send iPhone resale values south.

By the time Apple’s iPhone 4 launched in late June 2010, eBay resale values of the iPhone 3GS and iPhone 3G had dropped roughly 22% and 27% respectively, and they continued to decline until the middle of July. To make matters worse for iPhone owners planning to pawn off their phones, Apple is expected to unveil a new low-cost iPhone 4 model alongside the iPhone 5 in the coming weeks.

The draw of a brand new iPhone 4 available for $99 or less on contract — and possibly $350 with no contract in some markets, as BGR reported exclusively back in July — could potentially push the resale value of older models down even faster than last year.

Apple is expected to unveil two new iPhone models in the coming weeks, a low-cost version of the current iPhone 4 model with various minor design tweaks and a brand new iPhone 5 said to feature a new case with an aluminum back, a larger display and an 8-megapixel camera.

Zach Epstein has worked in and around ICT for more than 15 years, first in marketing and business development with two private telcos, then as a writer and editor covering business news, consumer electronics and telecommunications. Zach’s work has been quoted by countless top news publications in the US and around the world. He was also recently named one of the world's top-10 “power mobile influencers” by Forbes, as well as one of Inc. Magazine's top-30 Internet of Things experts.