Apple might be able to sell its iPhone and iPad lines in “small, medium, and large” in 2015. The iPhone in 4 inch coming back.
4 inches diagonal is the new pattern display size for the low-cost smartphones which allows your horizontally opposed thumb to be able to reach all four corners of the screen.
That is a strong reason as well, why Apple might include with iPhone 6 and iPhone 6 Plus succesors the 4 inch option with a similar design to the iPhone 5S but with the edges of the screen slightly curved to look like the actual iPhones 4.7 and 5.5 inch ( 6 and 6 Plus)
The new 4 inch iPhone smartphone will be in the "low end " category and will come up with low cost components to keep the price down, as all the Apple competitors are doing this way a long time ago now.
By the way the iPad line will arrive in Mini, 8.9 inch and a bigger sized model 12.9 inch.
We finally conclude Apple might be able to sell its iPhone and iPad lines in “small, medium, and large” in 2015, as well.