PhD students are already using AI models to work for them. Most of the PhD candidates I know have $200 Claude Max plan which they use to their fullest.
I see that they are able to do researches that they were not previously able to do. And although I see that using AI has certainly diminished their ability to code some stuff up, I see it the same way as someone using scikit-learn or Pytorch to code their ML models -- indeed the underlying details is abstracted away from you, and without AI, you won't be able to do much, but the research that you do is indeed happening because of you and wouldn't have happened with just the AI doing the research.
I see that they are able to do researches that they were not previously able to do. And although I see that using AI has certainly diminished their ability to code some stuff up, I see it the same way as someone using scikit-learn or Pytorch to code their ML models -- indeed the underlying details is abstracted away from you, and without AI, you won't be able to do much, but the research that you do is indeed happening because of you and wouldn't have happened with just the AI doing the research.