The much awaited release dates of the iPhone 6 and Galaxy S5 appear to be taking definite form this week as the international phablet market that the two devices are geared to invade is reportedly set to expand by up to five times from its current size.

As speculations stirred up that the Galaxy S5 will debut by late February 2014 with the actual release date to follow by April, Apple's rumoured first phablet is likewise projected to hit store shelves worldwide by June of the same year.

While the two tech titans do not officially dub the iPhone 6 and GS5 as phablets or oversized mobile phones, experts generally regard the upcoming gadgets as the next phablets to watch for. The Galaxy S5 is said to sport a 5.2-inch display panel while screen size for the next iPhone is tipped between 4.5-inch and 5.7-inch.

Note too that there are reports of two possible iPhone 6 models - one with a 4.7-inch screen profile and the other at 5.7-inch.

The separate launch dates, according to Gotta Be Mobile, came from known industry insider Eldar Murtazin.

But what is notable about the rollout timing is the fact that research firms are looking at incredible growth numbers for the phablet market in the next four years. From BGR, Juniper Research is forecasting that by 2018 some 120 million phablets will be shipped out.

In 2013 alone, 20 million phablets managed to hit the market, said the same report, which suggests that between now and 2018 this smartphone segment will experience incredible expansion, leapfrogging from the present level to as much as 500 per cent.

With the enticing numbers dangling before it, Apple is only expected to finally take the plunge and join the phablet competition this year. Apple watchers are hopeful that by May 2014, the tech giant will preview its first supersized iOS smartphone.

Talks are rife that just before the end of Q2 2014, a 4.7-inch iPhone 6 will break into the scene, to be followed, likely in September, by its larger sibling at 5.7-inch.

As for the Galaxy S4, the device is near the screen dimension that is considered as phablet-size at 5.2-inch. Take note that Samsung's original phablet, the Galaxy Note, was introduced in 2011 boasting of nearly the same display spread.

The same Juniper report indicated too that phablets will gain immense popularity in many Asian markets and foremost of which is China.

As Apple is gradually taking a foothold in the lucrative Chinese market, which is poised to become the biggest smartphone destination anytime soon, analysts are becomingly more convinced that the company is upsizing its iOS smartphone screen beginning with the iPhone 6.

So with the iPhone 6 and Galaxy S5 release dates probably touching down in the first half of 2014, the race is on for the two titans to deliver innovative phablet features.