In the full Q&A, she definitely hints at that. She says that people should be asking what Voldemort did to ensure immortality. She adds that she doesn't know whether anyone could guess the answer, but that's what should be asked.
The full Q&A can be found at JK Rowling's site (
http://www.jkrowling.com/en) in the "News" section. In this interview, she states, among other things, that Dudley is just Dudley -- nothing more to him. Aunt Petunia is not a squib, but there is a little more to her, which we shall learn in time.
Speaking of Rowling's site, the "Do Not Distrub" sign is gone, but there is only darkness behind the door. Anyone been able to find more?