Will the Samsung Galaxy S4 eclipse the iPhone?

As a venue for America's Grammy music awards, the Radio City music hall in New York has showcased stars from Michael Jackson to Lady Gaga, but on Thursday the headline act will be the world's next blockbuster smartphone.

At a ceremony to be broadcast live in Times Square, South Korean electronics giant Samsung will unwrap the Galaxy S4, its answer to Apple's latest iPhone and the latest salvo in the battle for supremacy between Seoul and Silicon Valley. Samsung already sells more smartphones than any manufacturer, but at the high end of the market Apple has remained unchallenged – until now.

Forecasters say Samsung's flagship Galaxy S franchise is catching up with the iPhone, and could begin to take its number one spot this year. While Apple has been weakened by rows with shareholders, trouble at its Foxconn factories and the maps debacle, the Samsung brand is gaining ground, backed by a $5bn-a-year electronics advertising budget that dwarfs those of all its rivals.

"Apple is not the one leading the market," said Francisco Jeronimo from analysis firm IDC. "I wouldn't be surprised if the new Samsung device sells more than the new Apple device over the next two years." Samsung's lips are sealed but it is ploughing every resource into packing the latest technology into the fourth edition of its Galaxy S, which is predicted to allow the users to scroll the screen and pause video simply by moving their eyes.

A camera tracks the gaze, which in existing Galaxy phones is already used to stop the screen going dark while pages are being read, and to adjust the picture to the viewer's line of sight. Trademarks called "eye scroll" and "eye pause" were registered by Samsung in Europe in January, suggesting two new functions.

The latest model is understood to have a 5in display, 13 megapixel camera and even an eight-core processor – today's most advanced phones have four cores in their silicon chips. All of which means the S4 should have a bigger screen, take crisper pictures and process web pages faster than the iPhone 5.

Samsung has "enormous" plans for the handset, according to Peter Misek at Jefferies bank, with orders for 100m in its first nine months. By comparison, Apple's bestselling phone to date, the 4S, took 15 months to ship 110m units by the end of December.

The scale of Samsung's ambition could pose more than a marketing threat to Apple. Competition for raw materials and components such as screens in the soaraway smartphone industry is fierce, and demand from Samsung is leading some suppliers to say they will reallocate resources away from Apple, Misek said.

In a move that could take the wind from the sails of Samsung, Apple is thought to have brought forward the launch of its latest phone. While the iPhone 5 went on sale in September, word on the street is that a 5S will appear this summer. Before that, the S4 is predicted to unseat the iPhone 5 as the world's bestselling mobile this spring, according to Neil Mawston at Strategy Analytics, who forecast supremacy would swing back and forth before a decisive blow is dealt.

"It's a bit like the Wacky Races at the moment, one company pulls ahead for one quarter and the other pulls ahead the next," he said.

Teaser video advertisements for the forthcoming Samsung "unboxing" feature a boy whose face is lit up by a golden glow as he becomes the first to lift the lid on the S4. The ad grandly claims he is about to witness "one of the most amazing products to hit the market since TVs went colour".

The pressure is particularly intense for Apple, whose latest products have been seen as lacking the wow factor that abounded when Steve Jobs was at the helm. "There is a lot of negativity around their brand at the moment," said Gartner analyst Carolina Milanesi. "The next iPhone is a crucial product but I can't see them not stepping up to the plate."

She predicts Apple will come back with a redesigned user interface, and extras such as more free storage for films in the cloud, a beefed-up version of its Siri voice-activated assistant and perhaps a price cut.