No official confirmation from Apple is out yet, though it is widely rumoured that the next iPhone iteration will be out as early as Sept 21, at least in the North American market, sparking a frenetic race for current iPhone owners to dump their old units for some cash.

The extra bucks should at least shave off sizeable amount from the budget of consumers planning to upgrade as soon as the first batch of iPhone 5 deliveries were stack on store shelves.

Tech news sites are in agreement that the best time to sell old iPhone models is now or more than a month prior to the Sept event that Apple will hold, details of which have remained under wraps though many are convinced that the tech giant will mark the occasion as the launch date for its iPhone 5.

According to CNET, iPhone owners who decide to take the plunge now can get as much as $US263 for their pre-owned units so long as they are close to brand-new state and carry at least 16GB of storage capacity.

That specific benchmark is currently in the menu of old-gadgets trade-in site Nextworth, CNET said, which also reminded that as Apple's D-Day for the iPhone 5 nears, the likelihood of attracting the highest bid is diminished.

Basing on the value decline model registered by the iPhone 4 prior to the iPhone 4S launch in October last year, previous Apple smartphones lose an average 12 per cent of their original value each month from the original date of purchase, according to Nextworth's Jeff Trachsel.

Roughly two months from the actual new iPhone roll out, some 25 per cent value of pre-owned unit would have been lost, Mr Trachsel told CNET, making the case for pushing out that old iPhone as hastily as possible much stronger.

In similar site like Gazelle, The Huffington Post reported that the retreat trend was pretty much the same but the exact iPhone unit appraised by Nextworth was priced a bit higher at $277 as of this week.

The relative high price that users can recoup from their ageing iPhones could convince owners to take the plunge now but Mr Trachsel noted that couple of things must be considered first.

If one particular Apple fanboy would sell his iPhone within this week, he faces the prospect of being locked out of the Apple universe until Sept 21, with the aggravating thought that new iPhone's actual sale date normally comes a few weeks after the launch date.

To squeeze into the best scenario there is, iPhone owners can wait for a couple of weeks prior to the Apple event and toss their units for sale while availing of the lock-in price offering that in Nextworth lasts for 21 days.

In Gazelle, the same deal is extended nine days more, the site's Anthony Scarsella told The Huffington Post.

Both arrangements provide for old iPhone sellers to hold on to their devices for a little bit more and enjoy at the same time the prevailing price at the moment they have inked the deal.

Bottom-line is current iPhone owners will be in the best position to determine on how and what manner they would want to dispose of their old units while collecting bits of 'discounts' in laying their hands on the next hot gadget in Apple's pipeline.

For those unwilling to part too soon from their handy Apple device and wait out for the actual roll out, Mr Trachsel noted that they can take comfort on the fact that iPhone still commands the best price bid for any smartphone brand out in the market.

The lowest iPhone 3GS configuration currently sells at $US80 in the trade-in market, the Nextworth chief marketing officer told CNET, which leaves the impression that later editions will lure more cash.

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