Check out the group of people determining it at the National Academies.

There are two problems, and they’re old ones. First is the lack of commercial industry participation. They’ve added former astronaut Bob Crippen who’s now at ATK, but that hardly counts. But the more fundamental issue (and reason for the first problem) is the assumption that NASA’s strategic direction should be established by the National Academies, with its own inherent assumption that it is about science and technology development, and not opening a frontier. This in turn may be another remnant of the agency’s beginning in the depth of the Cold War and the Space Act. But somehow, we can never have a serious national discussion about why we spend billions of dollars on human spaceflight, which will be necessary to get a new direction. And part of that discussion should be NASA’s role in the twenty-first century, and what other entities may be required as well.