Apple left the 4-inch screen model after successfully integrating the bigger 4.7-inch and 5.5-inch displays in iPhone 6 and iPhone 6s series. But the Cupertino tech giant isn't willing to let go of the popular 4-inch screen size, as leading analysts predict a 4-inch iPhone coming as soon as early 2016.

"As there is still demand for a 4-inch iPhone, we believe Apple will upgrade this product line. Because the iPhone 5s is more popular than the iPhone 5c, we think Apple is likely to launch an upgraded iPhone 5s. We predict Apple will mass-produce this new 4-inch iPhone in 1H16 with metal casings. In order to make the current iOS 9 or next-generation iOS 10 run smoothly, Apple may adopt an A9 chip for this new phone," MacRumors quoted KGI Securities analyst Ming-Chi Kuo as saying.

While some key elements of the unannounced 4-inch iPhone were revealed, Kuo also predicted that the popular 3D Touch feature will not be included in the small iPhone. With a launch date set during the first half of next year, the upgraded iPhone 5S will serve as a budget smartphone. According to Kuo, 20 to 30 million units of the new 4-inch iPhone will be shipped throughout 2016.

Apple's plans to release a 4-inch iPhone are no secret. There were several rumours hinting at an iPhone 6C with a 4-inch screen set to be launched during Apple's September event. With the new source in light, rumours about the much-popular 4-inch iPhone are back. 

For a long time, Apple reserved the screen size of its iPhones to 4 inches, even though rivals such as Samsung, Sony, LG and others moved to a larger size. Apple managed to keep up the demand for 4-inch screens over the years, which customers applauded for the handy and comfortable design. Things changed when Apple released the iPhone 6 and iPhone 6 Plus with bigger displays.

Other specifications of the unconfirmed 4-inch iPhone still remain a mystery but considering a "budget smartphone" tag, we expect the changes to be minimal. The new iPhone will succeed the iPhone 5S design, which means the features will be comparatively greater than the successful 5S.

Kuo also made some predictions about the iPhone 7 and iPhone 7 Plus; the handsets will continue to feature 4.7-inch and 5.5-inch screens, respectively. But the 2016 flagships, set for a release in September, will get a new A10 chipset and upgraded 3GB RAM.