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 a decade, 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. 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.