New Yorker cartoonists could have grounds for a “right of publicity” case, a body of state-based law that protects individuals from the unauthorized use of their name or identity. For that, there would need to be proof that the AI-generated cartoons were used for a commercial purpose, not just as a joke or gag.
I would have thought the fact OpenAI is commercially selling these forgeries (in exchange for subscription payments) would make that fairly straightforward to prove.