I played with it for a few days. It’s no threat to Unreal or Unity, at least at this stage.
Stingray can frighten Unity a lot because the offer 30$ with Maya included is a great offer that can attract many people using Unity Pro for 75$ a month.
Also i know some people using Probuiler with unity that will use Stingray because Maya is lot better than Probuilder.
But Unreal 4 is a too massive giant for Autodesk 