As the clock ticks down to Apple's much-awaited iPhone announcement, rumours are flying about the features the newest additions to the family will possess.

It is expected that the latest instalments to the series will be called the iPhone 7 and the iPhone 7 Plus, as per Apple's naming tradition.

There is speculation there may be a third addition to the set called the iPhone 7 Pro, but it is unclear how much credence these rumours hold.

The official launch is expected on Sept 7, with pre-orders starting Friday (Sept 9), and an expected release date of Sept 16.

The iPhone 7 is expected to have a 4.7-inch screen, while the iPhone 7 Plus and Pro models may have 5.5-inch screens.

The newer models may lack the antenna lines that run across the back of previous models, but are expected to retain the rounded-edged design as their predecessors, according to TechCrunch.

Apple's camera performance has long been a major selling point for fans of the phone. The latest additions to the family may have 12 MegaPixel cameras, with the larger model(s) possibly housing a dual rear camera.

According to MacRumors KGI Securities Analyst Ming-Chi Kuo ─ who has a 'solid track record' when it comes to iPhone rumours ─ claimed one of the phones may have a wide-angle camera with larger pixel sizes, a 6P lens and optical image stabilisation, whereas the other will have a telephoto lens with smaller pixel sizes and a 5P lens.

The difference in camera could impact the larger phone's pricing by as much as $40, Kuo said.

The iPhone 7 and iPhone 7 Plus models are both expected to carry an upgraded rear camera flash, with four LEDs ─ two of which provide warm light, two of which provide cool light ─ for better flash quality.

The iPhone's camera has previously been criticised for sub-par performance in low-light conditions. The newer models may feature upgraded ambient light sensors for better low-light performance, Forbes reported.

The company may be moving away from the traditional 3.5mm headphone jack with their latest iterations of the iPhone.

Reports suggest that iPhone 7 owners may have to use wireless headphones or use an adaptor that will allow them to plug headphones into the iPhone's Lightning Port.

A leak suggests that a pair of Lightning-connected special Apple earbuds will be included in the iPhone 7 retail box.

Rene Oehlerking, chief marketing officer of Jaybird, a company that makes and sells wireless headphones through the Apple Store, stated in a talk with Forbes that such a move would be in line with Apple's strategy and legacy of innovation.

One advantage of removing the 3.5mm jack is that it may provide consumers with better quality audio. But on the other hand, such a move may alienate users who do not want to bother with purchasing special Lightning-connected or Bluetooth-enabled headphones.

The new iPhone models are rumoured to have a base storage capacity of 32GB, twice as high as the 16GB offered on previous models.

A 256GB storage capacity is expected to be the upper limit, with the mid-tier storage capacity falling at 128GB on all models of the new iPhone.

The iPhone 7 Plus and Pro are expected to have 3GB of RAM, while the iPhone 7 will continue to include 2 GB.

All models may be powered by a new A10 chip with processing speed of 2.4-2.45GHz.

Rumours suggested a steel blue variant of the iPhone was going to be released.

These reports have been debunked after evidence surfaced claiming the variant was a 'mock-up' developed by a Chinese manufacturer.

Fans can still expect to see five variants of the new phone in the market: glossy Piano Black, Dark Black, Silver, Gold and Rose Gold. The Space Grey variant may be discontinued, Forbes reported.

Another development is the possible inclusion of a 'True Tone' display on the newer iPhone 7 models.

True Tone was launched with the iPad Pro 9.7. The feature allows the screen to dynamically change the white balance to suit the environment.

Apple may also be working on getting both handsets up to 1080p sharpness, with a rumored move towards glass-on-glass screens that may allow the iPhone 7 to provide a QHD or even a 4K display.

The newest iPhones may have improved IPX7 water resistance, rivaling those of the Apple watch, making the smartphones 'splash proof' but not fully waterproof, as is the case with the newly-released Samsung Galaxy Note 7.

Speculation abounded about the iPhone's water-resistance capabilities since Apple had filed paperwork for a patent that could pave the way for truly waterproof devices back in June 2014.

However, it is believed that the waterproof feature was rejected in favour of a slimmer phone body with only slight modifications required in the existing metal chassis.

The home button, a central feature in all previous iPhone models, may be in for a redesign as well in order to better support the improved water-resistance of the phone.

The new model is expected to have a pressure-sensitive sensor that will work simply by touch in place of the clickable button.