i thought they were already working on cyberpunk, how would they make an enhanced edition?
Roughly, they can take the state of the art engine they are making for CP2077 (using Vulkan for example), convert all the shaders from TW3 into compatible shaders for the new engine (may be using something like this which can eventually surface up), and assuming they won't be creating a new scripting language from scratch, they can just re-use existing Witcher Script programs from TW3. Voilà, you get an EE which can have better performance and is cross platform unlike stock TW3. Of course all that is very rough and high level. There can be tons of issues along the way which we don't know about. But it is feasible if they are interested in doing it.