Two 5.5″ models of the Zenfone series are already official, but a leak points to an incoming 5″ device.
The Asus Zenfone 2 ZE500CL is Intel Atom based and has 2GB of RAM. This will run Android 5.0 Lollipop and bring an 8MP camera with 1080p video and a 2MP front camera. The 5″ IPS LCD screen will have 720p resolution.
This device will have 16GB of expandable storage, a single microSIM slot with LTE connectivity and a non-removable 2,500mAh battery.
All of this informations are unofficial, so we have to wait for the mWC in March to see this smartphone.