iPhone 6 release date may happen after a year, according to a report of Forbes.

The report claimed that Apple is targeting September 2014 for the major upgrade of the iPhone 6. The report said that the weak sales of the iPhone 5S and 5C could be an advantage to the iPhone 6 release date.

Previous reports claimed that iPhone 6 release date will happen in the first quarter of next year. Some reports said that iPhone 6 will be launch in March.

Forbes is also certain that Apple will increase the screen size of iPhone 6 backed by the note of the market research company DisplaySearch to investors. DisplaySearch said that it reached out to sources from the Apple supply chain who claimed that the iPhone 6 will pack a screen display that is 5.7 inches in size.

"Introduction of the iPhone 5S and 5C was the latest example that Apple has been slow in adopting the latest display technologies. While 5-6" FHD resolution displays are rapidly growing in the smart phone market, the iPhone has stayed with the 4" 1136×640 screen for over a year and a half. [...] Based on supply chain research, we believe Apple is planning to revamp nearly all of the displays in its products over the next year," David Hsieh wrote in his note.

Other analysts also said that iPhone 6 will pack a larger screen. Jefferies & Co. analyst Peter Misek wrote in his latest note to investors early this week that the next iPhone 6 will pack a bigger screen display. He noted a deal between Apple and one of its suppliers to make this possible. KGI Securities analyst Ming Chi Kuo also said that iPhone 6 with bigger screen display is on the works.

It is speculated that iPhone 6 will be Apple's "phablet" flagship phone. This is probably true if the new smartphone will pack a 5.7 inches screen display, which is one inch less than iPad Mini and the same size as Samsung Galaxy Note 3's.

Aside from larger screen display between 4.8 to 6 inches, iPhone 6 features may also include a 64-bit A7 processor, M7 graphics chip, Touch ID fingerprint sensor and iOS 7 like the recently released iPhone 5S.

The upcoming iPhone 6 may also pack new features such as NFC and internal storage of up to 128GB.

However, Apple has not confirmed yet the rumours on iPhone 6.