Apple has not confirmed the truth behind the successor to last year's iPhone 6 and iPhone 6 Plus. Speculations have predicted that the Cupertino giant follows the current flagship with an iPhone 6s, while some have indicated that a numerical jump to iPhone 7 is more likely. Regardless, the latest iPhones continue to gain traction, kicking off with record-breaking pre-order sales at launch.

While we're waiting for official information, let it be known that there are four versions of the successor rumored to follow the iPhone 6 / 6 Plus. The iPhone 6s appears to take the form of a standard model, but there are also citations about an iPhone 6s Plus and an iPhone 6s mini. Finally, the iPhone 7 rounds up this list -- and they're all expected to launch soon.

iPhone 6s

One of the alleged specs of the iPhone 6s is the A9 processor, wrote Digital Trends. The chip was noted to be a collaboration between Apple and rival Korean tech giant Samsung. As told by the outlet, the processor is set to consume 35% less energy, while bringing 20% more power. It is based on a 14nm FinFET technology.

More recently, rumors have it that the iPhone 6s will pack 2 GB of LPDDR4-based RAM, Mashable reported. This seems to be a clear jump from the iPhone 6, which only had 1 GB of LPDDR3-based RAM. If the speculation holds truth, we're bound to see a faster iPhone that potentially rules out -- or diminishes, at least -- sluggish launching and multitasking.

As told by Forbes, these upgrades tie "nicely" with the advent of the iOS 9. In another report, the source took note of a leak surrounding the operating system.

Citing Google Analytics data of tech site letemsvetemapplem, Forbes felt that Apple has been working hard on the next major OS. Considering the company's annual release schedule (July - August), it's not surprising to find out that the iOS 9 is underway.

Indeed, Tech Times pointed that the iOS 9 may be an "extensive upgrade," contrary to the iOS 8 which brought more "minor tweaks and additions."

The iPhone 6s was also rumored to pack an OLED and 3D display, Android Origin reported. International Business Times took note of reports, which placed the iPhone 6s at a more affordable price than the current flagship. At present, the iPhone 6 starts from $199.

iPhone 6s Plus

The iPhone 6s Plus is undoubtedly larger than the iPhone 6s. Not much is known about the device, but it's touted to share similar specs as the latter. Rumored specs include a DSLR-quality imagery (two-lens system), wireless charging, sapphire glass and a "vibrating motor" safety feature, the Telegraph cited.

iPhone 6s mini

The iPhone 6s mini is said to be a 4-inch version of the iPhone 6. Slashgear expected the device to release "in the future."

As we have previously covered, reports claimed that 10 million units of the iPhone 6s mini are bound to hit the market. The handset is also expected to sell cheaper than the current iPhone 6.

iPhone 7

According to Know Your Mobile, reports indicated that iPhone 6s might arrive in the first half of 2015, alongside the Apple Watch. The iPhone 7, on the other hand, was suggested to take a late Q3 launch.

Just like the iPhone 6s, the iPhone 7 is claimed to pack 2 GB of RAM. Macworld reported that the device could be thicker than the iPhone 6, citing the possible inclusion of "sidewall displays," sapphire glass and liquidmetal chassis.

In addition, The Fuse Joplin cited rumors, which claimed that the iPhone 7 will be waterproof and powered by solar technology.

Note that there were reports about an iPhone 6c and an iPhone Air, but just like the rest, no official confirmation has been announced yet.