As far as we know at the moment Moto E3 will be smaller brother for G4 Play Plus (same design): 5" 720p screen, Android 6.0, 8MP rear cammera and 5MP front one, 8GB internal memory and quad-core 1GHz MediaTek CPU.
As I said, they wil look identical excluding size - E3 will be smaller.
Both will be launched next month probably for £100 and £130 so around $132 and $171.
Source: GSMArena