The iPhone 6 and 6 Plus have both been around long enough to consider them part of the furniture. But we know that Apple updates the iPhone annually, and the next model is just around the corner.

Will the next-generation iPhone be called iPhone 6S or iPhone 7? Will there be an iPhone 6S Plus or iPhone 7 Plus instead? Will any of these phones feature an entirely new camera?

There's never a shortage of speculation when it comes to the next iPhone. We've drilled through all the rumours to bring you the best picture of what the next model will offer.

Apple typically names each generation of products by either a flagship feature or design change, according to Tim Cook, the company's CEO. The iPhone 6 Plus, for instance, has a larger screen, so it has a "Plus" moniker for having a plus-sized screen.

If you go way back, the iPhone 4S got the S moniker because it debuted with Siri. And even further back, the iPhone 3GS came with added speed thanks to a better processor over the 3G. For the next iPhones to have an S name, they will have to sport something that make them standout, but if they stand out too much, sort of like the iPhone 6 handsets do, they'll get all-new name like iPhone 7.

There are rumours that claim Apple wants to drop the S name altogether because it carries a mediocre connotation, but that's not confirmed.

At the end of the day, everything is speculation until Apple confirms. But we're going to call the next iPhone the iPhone 6S. There's even reports going around about an iPhone 6S Plus, so we'll also talk a little about whether that's legit.

Apple has just sent invites to the media, inviting them to attend its next iPhone launch event in San Francisco. Everything is scheduled to go down 9 September at the Bill Graham Civic Auditorium - a new venue for Apple.

In the actual invite, which sports bright colours reminiscent from from iOS 7/8, the company teased: "Hey, Siri, give us a hint". That suggests Apple's personal digital assistant might be a big focus. Apple will likely also announce when iOS 9 and WatchOS 2 will roll out. All of this is slated to kick off at 10am PST.

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Apple has confirmed that the event will be live streamed and you can find all the Apple Special Event 9 September 2015 details right here.

Also, a leaked email sent to Vodafone staff has indicated when the phones will appear in store: 25 September. Subsequently, however, we've seen availability mentioned as 18 September, with pre-orders opening on 11 September. One thing we know about iPhone is this: it always goes on sale on a Friday.

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The design, again, all comes down to the name. If Apple releases iPhone 6S and iPhone 6 Plus, they will likely only feature internal changes and may look a lot like the iPhone 6 and iPhone 6 Plus, respectively.

Leaked pictures of an alleged iPhone 6S shell suggest exactly that, as do schematics that turned up at Engadget Japan. These schematics suggest that the iPhone will be 7.1 thick, rather than the 6.9 of the current model.

According to The Wall Street Journal, which sourced unnamed Apple suppliers, Apple's next-generation iPhones will continue to be available in 4.7 and 5.5-inch screen sizes, with plans to "keep the resolution similar."

Apple Insider has also said the next-generation iPhones will retain the same physical design as the iPhone 6 and iPhone 6 Plus, including 4.7-inch and 5.5-inch models too.

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9to5Mac got hold of an iPhone 6S casing - and the rear shell appears to have the same exterior design as the current iPhone 6, including the same thickness and width. More leaked photos revealed the Lightning connector and other bits - such as the speakers, mic, headphone jack, volume toggle, mute button, sleep button, SIM card slot, and camera cutouts - are also identical to the iPhone 6.

Oh, and early reports suggested that Apple is considering a pink or rose gold version this time around too. It would complement existing grey, silver, and gold options.

It's expected that the iPhone 6S will have the same size and resolution of display as the current models. That would make the iPhone 6S a 4.7-inch device with a 1334 x 750 pixel resolution Retina HD display. The iPhone 6S Plus should come with a 5.5-inch 1920 x 1080 pixel resolution Retina HD display.

Leaker @KJuma claimed the iPhone 6S will feature a 4.7-inch screen with a 1125x2000-pixel resolution (488ppi), while the iPhone 6S Plus will have a 1242x2208-pixel resolution, resulting in 460ppi.

However, it's not just about the resolution of these displays. There have been a number of rumours that there will be a change of technology in the display.

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A screen technology that is likely to be used on the new iPhones is Force Touch.

The pressure-sensitive haptic technology knows how light or hard you are pressing or tapping the screen to open up an all-new level of interaction. It is being used by Apple on its Apple Watch and new MacBook. The Wall Street Journal has cited "people familiar with the matter" saying that Force Touch will come to the new iPhone, which makes perfect sense.

KGI Securities analyst Ming-Chi Kuo, who has a great track record at reporting on Apple rumours, has also claimed the next-generation iPhone will have a capacitive Force Touch sensor, and that the change may be significant enough for Apple to call its next iPhone the iPhone 7 rather than "iPhone 6S", according to MacRumors.

The analyst said this hardware implementation of Force Touch would be different than the technology used in the Apple Watch and 12-inch Retina MacBook. It won't directly detect the pressure applied by fingers, but it will monitor the area where a finger presses to determine pressure applied.

READ: What is Force Touch?

Apple's new Force Touch technology might be exclusive to the iPhone 6S Plus. Taiwan's Economic Daily News reported that Taiwanese manufacturer TPK will supply Apple with the Force Touch sensors, but it made no mention of just the iPhone 6S, meaning the technology might only go to the iPhone 6S Plus.

There's also the rumour that there will be "taptic" feedback from the display.

There's a rumour that suggests Apple might use the same 7000 series aluminum in the Apple Watch for its next-generation iPhone. This aluminium is lightweight and 60 per cent stronger than standard aluminium. It's also a lot more expensive and difficult to work with.

A video purporting to show the iPhone 6S casing in a bend test claims to reveal the 7000 series aluminium has been used by Apple for the new handset. In the bend test the iPhone 6S offers over double the strength of the iPhone 6. Check out the video.

The next iPhones will feature the "biggest camera jump ever" - and it'll even compare to DLSRs in terms of image quality, according to John Gruber, a blogger and podcaster who is notorious for having inside sources at Apple.

"The specific thing I heard is that next year's camera might be the biggest camera jump ever," Gruber revealed in a recent podcast. "I don't even know what sense this makes, but I've heard: it's some kind of weird two-lens system, where the back camera uses two lenses, and somehow it takes it up into DSLR-quality imagery."

Apple Insider dismissed the rumour about a dual-lens camera system, as such a feature would require redesigning the iPhone and ditching the current chassis found on the iPhone 6 and iPhone 6 Plus, which we don't think will happen.

However, the biggest jump ever part might be correct, with rumours that the iPhone 6S is going to move up to a 12-megapixel sensor. Sources inside the supply chain, cited by Business Insider, claim that there will be a new sensor allowing better capture of light, with a new five-element lens.

There's no mention if there will be a difference between the iPhone 6S and iPhone 6S Plus. We'd expect the same arrangement as currently, with the 6S Plus offering optical image stabilisation and the 6S not.

Apple usually gives "S" upgrades new features, such as Siri, Touch ID, new processors, and camera improvements.

Based on past updates, many have assumed the next-generation iPhones, especially if they are iPhone 6S and iPhone 6S Plus, will receive the new A9 processors produced by Samsung. Bloomberg has claimed Samsung will provide Apple with A9 chips for the next iPhones and other devices.

Leaker @KJuma posted a Geekbench score for the iPhone 6S, showing the phone running Apple's A9 SoC. The CPU was clocked at 1.8GHz. It also revealed 2GB of RAM.

Also, it's assumed the next iPhones will have 16GB, 64GB, and 128GB capacities.

That's it for now, but keep checking back for all the latest. We promise to update as more and more rumours surface.