While nothing is certain, months of rumours have painted a fairly reliable picture of not one, but two bigger, prettier iPhones. So here are the answers to some common questions surrounding what to expect.

Why are people so sure there'll be a 4.7-inch and a 5.5-inch screen size?

Since Japanese newspaper Famitsu first reported the two screen sizes in March – citing a source at a local display manufacturer – the figures have shown up in virtually every iPhone 6 rumour. The original report said the release could be staggered, with the larger 5.5-inch model being released after its smaller brother. Subsequent reports have echoed this.

It's not like Apple to announce a device without immediate launch plans, but reports of manufacturing issues for the 5.5-inch iPhone could also be a factor in a staggered launch. The larger displays also make sense given their huge popularity in Asian markets and almost standard five-inch to 5.5-inch screens of Android phones. The iPhone 5 screen is only four inches.

So when will I be able to get the iPhone 6?

Assuming Apple takes the same approach as last time, an iPhone announced on September 9 will be available 10 days later, on September 19.

Will it be called the iPhone 6? 

It seems likely given the company's recent naming conventions, with major revisions earning a new number (iPhone 4, iPhone 5) and smaller refinements or offshoots getting a letter (iPhone 4S, iPhone 5C, iPhone 5S ).

What hardware improvements are we likely to see?

Famitsu's original report said the iPhone 6 screen would be "significantly" higher in resolution than that of the iPhone 5S (which is 1136 x 640). This makes sense if the screen is larger and Apple wants to maintain its trademark "retina display" pixel density. A resolution of 1704 x 960 would be needed to give a 5.5-inch screen roughly the same pixel density of an iPhone 5, so expect that at least.

A better battery is almost a no-brainer. One report from AppleInsider claims new battery technology will allow the 4.7-inch iPhone 6 to achieve a 15 per cent improvement in performance over the iPhone 5S. Anyone wishing for a heavier 2500 mAh battery or a swappable battery, both features of Samsung's Galaxy S5, are likely to be disappointed as various sources point to the new iPhone being slimmer and sleeker than the last.

Expect obligatory improvements to the camera, processor and possibly the speakers as well, and don't be surprised if Apple finally makes the leap to including a near-field communication (NFC) chip on its phone to allow for mobile payments.

What about software?

You've already heard all about iOS 8, which will be launching with the new phones. Expect to hear more about health initiatives, connected-home features and what, if anything, has come of Apple's purchase of headphone brand Beats.

Will the new phone be hardier than previous iPhones?

One of the most persistent rumours has been that iPhone 6 will be covered in near-indestructible sapphire glass. Several online videos purported to show users bending, stabbing, scratching and hitting these displays to prove their worth. However while sapphire will still be used for the camera lens and home button, analysts recently said there had not been enough sapphire glass in the manufacturing supply chain to indicate the phone will be covered in it.

Some are adamant at least one of the iPhone models will use a full sapphire glass screen which, taken with the rumours about one phone releasing after the other, could point to a regular 4.7-inch iPhone followed by a premium, 5.5-inch, indestructible iPhone.

Will we see the iWatch on September 9?

Unlikely. If Apple is indeed having an iPhone event on September 9 (and if the past is any indication) they'll keep it focused on iPhones.

SMH