Here are the specs for the system that ran the game in the E3 demo:
CPU: Intel i7-8700K @ 3.70 GHz
MB: ASUS ROG STRIX Z370-I GAMING
RAM: G.Skill Ripjaws V, 2x16GB, 3000MHz, CL15
GPU: GeForce GTX 1080 Ti
SSD: Samsung 960 Pro 512 GB M.2 PCIe
PSU: Corsair SF600 600W

While there's no official statement regarding this, here's a rough estimate for the ideal spec (40+fps at 1080p):
Processor: Intel Core i5-6600K 3.5GHz
Graphics: NVIDIA GeForce GTX 1060 6 GB
System Memory: 8 GB RAM
Storage unit: 128GB SSD