It really depends what you consider AI. Content bots are already here on steem; Nobody seems to mind avoidable auto-generated reports. It'd be foolish to think that there weren't text generating AIs already assisting posters. I doubt there are any here that are sophistocated enough to be autonomous, but yeah, I wouldn't be surprised.
On the art thing; my claims that AI made some art are well overstated imo. Scratch the surface and you'll see that the AI is not much more than a smart paintbrush. I've been toying with a thought-experiment about what it would take for an AI to gain the status of co-author/co-creator but they still wouldn't be authors in their own right.