No. This question, and it’s a common one, assumes there’s a fixed number of students who will study on your programme at your institution. As the MIT study proves, OER can act as a powerful marketing tool to increase the pool of potential students thinking about studying at your institution.
The question also assumes that there’s a direct correlation between availability of resources on the web and student choice. In reality student choice is much more sophisticated and multi-modal. Students use the web in many ways to try to ‘personalize’ the future for themselves – they want to know what the experience of learning at your institution might be. If your name, associated with your resources and institution, is available on the web they will be discovered by potential students, and will give students an insight into your methods of teaching. And we know that many students are attracted by methods of learning that involve interaction and working with knowledge in practical ways.