System requirements for X-Plane 11 have just been announced!

Minimum Hardware Requirements:

CPU: Intel Core CPU (e.g. i3, i5, i7), 2 or more cores, 3.0 Ghz or faster, or AMD equivalent

Memory: 8 GB RAM

Video Card: a DirectX 11-capable video card from NVidia, AMD or Intel with at least 1 GB VRAM

CPU: Intel “Core” i5 6600K at 3.5 ghz or faster

Memory: 16-24 GB RAM or more

Video Card: a DirectX 12-capable video card from NVidia, AMD or Intel with at least 4 GB VRAM (GeForce GTX 1070 or better or similar from AMD)

Check out the full list of specs in this Knowledge Base post.