Something like this was already attempted about a year ago- https://www.roleplayerguild.com/posts/5476740

While it was an amusing experience (and quite a cool world setting), an AI like ChatGPT can only serve as a GM for so long until it starts having issues with remembering plot points/setting info/etc.

It's a nice tool for a GM, though, especially when it comes to world building and brainstorming character concepts.