With the Samsung Galaxy S4 commercial release already looming, another indicator emerged and declared that the iPhone 5S is almost upon us - sweet price cutbacks for currently the top-selling Apple smartphone, the iPhone 5.

U.S. gadget retailer RadioShack has started giving attractive discounts for the handset, $US50 to be exact and in exchange buyers will have to agree for a two-year contract with Sprint.

Along with the iPhone 5, RadioShack is also selling the iPhone 4S at more compelling price tag, actually getting the same price discount and sales condition - a $US50 price off plus tie in with a Sprint plan.

The promo runs on limited time only, according to CNET, and will end by April 4. So those holding off their iPhone buys for the longest time should better hurry as this is one of the better deals to come out in the months prior to the rumoured iPhone 5S release on the second half of 2013.

Note that unlike in previous handset deals that Sprint had concocted, the Apple smartphone sale is walk-in only so buyers need to head out for the nearest mortar & brick stations maintained by RadioShack.

And the likelihood is, they will stumble on an equally mouth-watering deal involving Samsung's outgoing flagship - the Galaxy S3.

The Android handset is now up for grabs for only $US50 - one of the lowest price levels attached to the premium smartphone to date.

Like the Apple offer, the Samsung deal comes with a Sprint locked-in agreement that is reserved for new subscribers.

On top of the price discounts, RadioShack also encourages people to hand in their old handsets, which would merit corresponding additional cash-backs. The value, of course, will depend on the state and brand of the gadget that will be surrendered.

More of these handset promotional sales are expected to appear in the months and quarters ahead as new gadgets geared up for market debuts. Apple is expected to issue the iPhone 5S, the iPhone 6 and a budget iPhone between June 2013 and January 2014.

Likewise, Samsung will unveil its next phablet offering, the Galaxy Note 3, which reports said will be uncloaked by September at the latest.

Nokia is also expected to refresh its high-end Lumia line - the Lumia 920 and the Lumia 820 - by Q4 2013.