iPhone 5se "special and enhanced" coming in 4 inch for late March.

Apple`s rumored  small size iPhone will not be a 6C model at all. It is coming as a "special and enhanced" (se) iPhone 5s as 5se with the following upgrades:

• The chamfered, shiny edges have been replaced with curved glass like on the iPhone 6 and 6s lines
• The same 8 megapixel rear camera and 1.2 megapixel front camera systems from the iPhone 6
• Support for larger panoramas and autofocus for video recording
• Barometer for tracking elevation in the Health app
• An NFC chip for Apple Pay
• The A8 and M8 chips from the iPhone 6
• Bluetooth 4.2, VoLTE, and 802.11ac WiFi chips from the iPhone 6s
• Live Photos from the iPhone 6s
• Same Silver, Space Gray, Gold, & Rose Gold color options as the 6s line.

No 3D Touch included.  Still include a headphone jack

Apple hopes that this model could spur additional upgrades over time from those currently sticking to an iPhone 5 or earlier. 

The current 5s will likely be discontinued, and the “5se” will take its place. The new device is currently in production overseas and is planned for a March introduction ahead of a late March or early April release.

9to5Mac