The countdown for the much-awaited iPhone 5S and iPhone 6 release date starts ticking as Apple and its retail partners begin the final push to clear out existing iPhone inventories through promo deals, highlighted by the $98 iPhone 5 at Walmart.

Walmart, according to CNET, joins the pack of U.S. gadget sellers trying to convince consumers that now is the best time to score the iPhone 5 and the iOS smartphone builds before it as tag prices are discounted to unprecedented levels.

The 2012 Apple hero phone, rolled out in October 2012, now sits on Walmart store shelves with less than $100 as its asking price. Previously, the retail giant priced the handset at $129 coming from its $199 sticker price, which comes with a 16GB internal memory, in black or white casing plus 2-year contract from AT&T, Sprint and Verizon.

And to further sweeten the already juicy iPhone deals, Walmart also offers the iPhone 4S for an irresistible $39, which for many buyers should be good enough as the model, issued in 2011, represents Apple's introduction of Siri - the iOS personal digital assistant - and a host of other significant jumps on iPhone features.

Yet for those on the hunt to secure the best buy possible, the iPhone 4, approaching its third year in circulation, is a definite lure at only 97 cents. Note, however, that these handsets - from the iPhone 5 down to the iPhone 4 - are rumoured to be on their way out, which means hardware and software supports should be hard to come by after a couple of years.

Apple is reportedly winding down the production of its legacy devices as the company shifts its focus on the iPhone 5S and the iPhone 5C, including the iPhone 6 that analysts said should be out by early 2014.

Prior to pushing its army of new iOS gadgets beginning Sept 2013, the tech giant is gunning to replenish its old iPhone and iPad stocks through its in-house swap deals that lure customers to surrender their working and still good-looking Apple gizmos for credits of up to $280.

The actual trade-ins started Friday, according to Apple Insider, and consumers can secure gift cards by proceeding to any Apple Stores located across the United States. Credits obtained can only be used on the purchase of brand new iPhones (with contract), iPads and iOS gadget accessories.

These wholesale deals, analysts said, trumpet the fast-approaching 5S and 5C release, an event seemingly confirmed as Apple starts limiting the vacation leaves given to its frontline employees - staffs to man Apple Store and AppleCare.

In a separate report by Apple Insider, time offs for these Apple workers will be restricted from Sept 15 to 28, which falls within the Sept 20 schedule believed as D-Day that consumers can start grabbing the new smartphones. Earlier reports have suggested that Japanese and U.S. buyers will have initial access on the iPhone 5S and 5C on the same day.

On release date, the iPhone 5S is expected to sport the same iPhone 5 look but with significant component upgrades inside and out with the iOS 7 delivering the so-called killer features. The iPhone 5C, on the other hand, is seen to come out in plastic casing and is packaged as the more affordable build.