So much has been leaked about Apple's upcoming devices dubbed as the iPhone 6s and iPhone 6s Plus ahead of their release. Amid all the hype around them, Apple fans and prospective buyers could be left disappointed when they are released.

The Cupertino-based giant is expected to unveil the next iPhone devices at its scheduled event on 9 September in San Francisco. To be precise, it is just eight days to go before the devices are launched. Despite all the hype and hoopla around the iPhone 6s and iPhone 6s Plus, two features of the devices have the potential to upset Apple fans, according to reports.

The iPhone 6S is expected to house a 1,715 mAh battery against 1,810 mAh seen in the iPhone 6, and the iPhone 6S Plus is expected to come with a 2,750 mAh battery as against 2,910 mAh seen in the iPhone 6 Plus, according to a report by cnBeta (via Forbes).

It may be just a 5.3 percent decrease for the iPhone 6S and 5.5 percent decrease for the iPhone 6S Plus but Apple fans and prospective buyers won't be happy if such a thing happens, as Apple devices are already known for short battery life. In fact, if there is one feature that needs a drastic upgrade in future iPhones, it has to be battery.

Another feature that could disappoint Apple fans is the dimensions of the upcoming devices. MacRumors has reported citing sources that iPhone 6S is thicker than iPhone 6, a 0.2 mm increase in overall thickness to be precise, possibly due to Force Touch technology to be introduced in the device. It went on to report that the upcoming device weighs 51.2 grams compared to iPhone 6's 49.4 grams. 

The new report is in sync with earlier claim by M.I.C. Gadget that reported that iPhone 6s is 7 mm thick (6.9 mm thick in the iPhone 6) and iPhone 6s Plus is 7.13 mm thick (7.1 mm thick in the iPhone 6 Plus). 

The changes in battery and dimension of the upcoming iPhone devices may be negligible but gadget lovers might still complain.

Well, iPhone 6s and iPhone 6s Plus are expected to have similar features except for the display with the former likely to sport a 4.7-inch screen and the later a 5.5-inch screen, according to reports. They are expected to house A9 chip, iOS 9, 32 GB internal memory, 2 GB RAM and 12 MP main camera under the hoods.