If any currently existing game were to implement effective AI dialog systems it would probably be Dwarf Fortress. Though there are some issues.
The Program would probably need to be built from the ground up. Trying to implement Chat GPT or some other pre-existing text-generative ai would lead to problems as they aren't built to work with Dwarf Fortress. You have the classic "As an ai language model..." which could rear its ugly head whenever you said you wanted to do something unethical in-game. Less obvious is that Chat GPT is built to give accurate information about the real world and doesn't actually know much about what goes on in Dwarf Fortress so it might just assume incorrect things such as all dragons having wings, elves not cannibalizing people they slay in battle, and what some of the hidden fun stuff is like. Using another generative AI could also work but they all have unique issues, so the only good option would be to make one built for dwarf fortress, possibly taking not only the user's text but also the stuff around as inputs, which is kinda annoying. Rudimentary AI generally speaking isn't too hard to get up and running(though generative ones are a lot harder), with the use of libraries it becomes pretty easy, but it takes a long time to train and if you're trying to do something new with it, such as implementing it into one of the most complex games ever created, then you'll probably need to try a lot of testing and tweaking for someone who already has a ton of experience with AI. While Toady has done some crazy things, I'm pretty sure this would take him way longer than is worth it to actually implement. Games like Façade have done this kind of thing since the mid 2000s with mixed results so it's totally possible, though in order to achieve that they had to cheat a lot to get the AI remotely coherent and they were also built to make it as easy on the bot as possible and while the former is doable the latter is a bit harder since the game is already made and full of complications that the AI needs to take into account and interpret. Façade takes place in a single room and has two characters, dwarf fortress is a massive open world full of conflicts and events. Like when you're in a tavern and there's like 20 random people around doing their own thing, with tavern brawls going on, people passing out, and you ask a dwarf who happens to know a few historical figures a series of broad, subjective, and open ended questions, the AI bound to get some stuff jarringly wrong and completely break the emersion you had. It's theoretically doable, just really hard. IDK if any of that made sense but I think it got some general points across, I am not very good when it comes to describing this type of thing.
TL;DR: AI is a fickle beast and while it's not hard to make and train an AI, making one that interacts well with the systems in DF is a lot harder.