https://www.thegamer.com/the-witcher-4-unreal-engine-5/ I wonder what their motivations were. Most likely after the release of Cyberpunk 2077 and the associated costs, projections further development and maintenance costs of REDengine would be higher than the licensing costs for Unreal Engine 5. Though personally I abhor CDPR's tendency to employ Crunch in their development, I hope that they can bring some useful expertise to Unreal Engine 5 for open worlds. And since Unreal Engine has been growing quite a bit in the recent years, they've a larger pool of developers they can potentially recruit from.