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.