When the brand new Witcher game was announced yesterday — developed using Unreal Engine 5 — CD Projekt Red also clarified that Cyberpunk 2077's upcoming expansion will still use the studio's in-house REDengine. However, the company's statement on the matter has raised some eyebrows because of its use of "expansion" rather than "expansions".
So yeah, it's a bit weird that CDPR is specifying 'expansion' rather than 'expansions'. We're sure all will become clear in the relatively near future, but in the meantime, we've reached out to CDPR for clarification. We'll update this article if we hear anything back.