I think Bravo Delta stands for "Bigger Display" and it will focus mainly on electronic textbooks. That would be in accord with the upcoming release of NOOKstudy, a pc software developed by B&N for students and universities.
B&N is trying to move into the e-textbook market and it would make sense for them to launch a bigger e-ink reader.
http://www.barnesandnoble.com/nookst...4266-_-Primary