Jefferies analyst Peter Misek says that there will be a June 2014 releasefor the iPhone 6. We reckon it will be later than that, around a year after the 5S. Citi's Glen Yeung also believes that we won't see an iPhone 6 until 2014, although that's no big leap.
Interestingly, in May 2013 Stuff reported it received a photo of the till system at a Vodafone UK store (which it has since removed along with the reference to Vodafone), with '4G iPhone 6' listed.
So could we see both an iPhone 5S and iPhone 6 in quick succession?Some reports suggest a new 5S in the late part of the year before a revamped iPhone 6 very early in 2014.

iPhone 5S
Apple may have a new roadmap, with new phones every spring and autumn

iPhone 6 casing

It's been suggested that there could even be three size variants of the new iPhone - check out these mocked up images by artist Peter Zigich. He calls the handsets iPhone 6 Mini, iPhone 6 & iPhone 6 XL (these look rather like the iPhone 5C variant though). However, as ZDNet rightly points out, different size variants aren't exactly easy to just magic out of thin air.

iPhone 5S
Pretty, yes, but also horrifically scratch-prone. Will your next iPhone have a plastic back?

The iPhone 6 will finally do NFC

About time too. Well, that's what iDownloadblog reckons, quoting Jefferies analyst Peter Misek. Many Android phones now boast NFC and Apple appears to have been happy to be left behind here.
See our video below on what Apple needs to do to slay Samsung's Galaxy S4

The iPhone 6 will run iOS 8

With iOS 7 heading out of the traps now, who's betting against the next iPhone coming with iOS 8?
We'd expect a September or October release date for iOS 8 in line with previous releases.

iOS 7: what do you think?

iPhone 6 storage

We've already seen a 128GB iPad, so why not a 128GB iPhone 6? Yes, it'll cost a fortune, but high-spending early adopters love this stuff.

iPhone 6 home button

According to Business Insider, of the many iPhone 6 prototypes Apple has made, one has a giant Retina+ IGZO display and a "new form factor with no home button. Gesture control is also possibly included". It will surely include Apple's new Touch ID finger print tech though?

iPhone 6 screen

The Retina+ Sharp IGZO display, would have a 1080p Full HD resolution. It's also been widely reported that Apple could introduce two handset sizes as it seeks to compete with the plethora of Android devices now on the market.
Take this one with a pinch of salt, because China Times isn't always right: it reckons the codename iPhone Math, which may be a mistranslation of iPhone+, will have a 4.8-inch display. The same report suggests that Apple will release multiple handsets throughout the year over and above the iPhone 5S and 6, which seems a bit far-fetched to us.
Patents show that Apple has been thinking about magical morphing technology that can hide sensors and even cameras. Will it make it into the iPhone 6? Probably not.
Jefferies analyst Peter Misek also says he believes the new iPhone will have a bigger screen. Different sizes also seem rather likely to us - theword on the street after WWDC 2013 was that there would be 4.7 and 5.7-inch versions.
More rumors in September 2013 point to a six-inch display, but this seems a little large to us.

iPhone 6 camera
You'll probably still be able to see the camera lens in the iPhone 6

iPhone 6 processor

Not a huge surprise, this one: the next processor one will be a quad-core A8 or an evolved A7. The big sell here is more power with better efficiency, which should help battery life.
Update: Anyone hoping for some juicy Samsung technology hidden under the iPhone 6 body will be disappointed though, as reports suggest Apple is looking to push its Korean rival further out of the iPhone picture with its eighth-gen handset.
Apple is apparently cutting the amount of A8 processors it is having made by Samsung, although it hasn't severed ties completely just yet.

iPhone 6 camera

Apple's bought camera sensors from Sony before, and this year we're going to see a new, 13-megapixel sensor that takes up less room without compromising image quality.
An Apple patent, uncovered by Apple Insider in May 2013, shows a system where an iPhone can remotely control other illuminating devices - extra flashes. It would work in a similar manner to that seen in professional photography studios. Interesting stuff.

Say Cheese to the iPhone 6
Will the iPhone 6 be handy for pro photographers? [Image credit: Apple Insider]

iPhone 6 eye tracking

One thing seems certain - Apple can't ignore the massive movement towards eye-tracking tech from other vendors, especially Samsung. It seems a shoe-in that Apple will deliver some kind of motion tech within the next iPhone, probably from uMoove.

iPhone 6 wireless charging

Wireless charging still isn't mainstream. Could Apple help give it a push? CP Tech reports that Apple has filed a patent for efficient wireless charging, but then again Apple has filed patents for pretty much anything imaginable.
The tasty bit of this particular patent is that Apple's tech wouldn't just charge one device, but multiple ones. Here are more details on the iPhone 6 wireless charging patent.
Meanwhile, a further Apple patent seems to imply that future iPhones will be able to adjust volume as you move them away from your ear.
And could the iPhone 6 really have 3D? It's unlikely, but the rumours keep on coming..