CD Projekt Red confirmed the news with Eurogamer, indicating it's more interested in focusing on future projects than returning to an old one.
"Since we want to fully focus on Cyberpunk 2077 and Gwent, and converting The Witcher 3: Wild Hunt from a full HD game into a 4K one would be too much of a time and resource-consuming process, we decided not to release an edition of Wild Hunt supporting the new features of PlayStation Pro," the company said.
Eurogamer points out that the game does offer 4K support on PC, though that doesn't mean that enabling it on PS4 Pro would necessarily be an easy task. This also doesn't rule out the possibility that the game will simply run better on Pro, as some Xbox One games do on the Xbox One S.
A number of existing and upcoming games are receiving support for PS4 Pro features, including 4K and HDR (which is now available on all PS4s), or improved visual effects and frame rates when playing at 1080p. Specifics for most of the games confirmed to receive Pro upgrades have not yet been announced, but we do know about a handful that you can read about here.