Here's one: how long until a computer can beat a human assisted by a computer?
More generally, scientists using AI for research will probably have to do research on the research, to understand what the AI discoveries mean. Maybe they mean something we can't grasp at all, in which case they go completely over our heads, like ants trying to learn about the finer points of financial markets. We will probably have to learn new concepts and even new languages designed by the AI to convey the meaning.
Here's a very good article: http://dustycloud.org/blog/sussman-on-ai/ (A conversation with Sussman on AI and asynchronous programming)