With enough time, resources and will, everything will be possible.

I wouldn't be surprised if the next iteration of text generators (in a few months) have the ability to do fully fledged adventure text games by writing the story first, with all it's possible outcomes and links between the text segments, then putting the segments inside a traditional text adventure shell program. Even if that AI then pipes that story or story portions into another AI text adventure software generator to output the program. If passing the Turing test is a few months away as hinted, then these would be possible and refined by the end of next year.

As to more advanced games? We'll be seeing feedback loops and exponential returns over the next few years that will see the development of AI generated games parallel the development of the history of video games, but in accelerated time; whether this will hit open world VR levels before we hit AGI (and everything accelerates) will determine if it is an exponential curve or a hyperbolic one.