Are we anywhere near someone being able to play a D&D or WoD type of game session with an LLM somewhere in the mix, perhaps generating a new and interesting adventure every time? Or is this still science fiction for now?

“Somewhere in the mix”? Sure. I’ve seen TTRPG folks experimenting with LLMs for about as long as LLMs have been around. A couple years later it still can’t really run a session, but you might find it useful for generating some details of an adventure.

The big issue really is making its output interesting. As usual, an LLM will default to the most generic outcomes and settings. For a TTRPG to be fun you usually want surprise, drama, creativity - it can’t do any of those.