You have said a couple of times in this thread that DB's almost never go in the top 5. I don't think that is very accurate. I think that it is somewhat cyclical. As the passing game becomes more and more effective teams start emphasizing the need for playmakers in the secondary. When offenses start running more then you start seeing more defensive linemen going early.
There have been defensive backs taken in the top 5 in the last two drafts. Before that was a stretch of several years where there weren't any taken real early. But then prior to that there was a several year run where they were. I think you will see corners and the occasional stud safety taken high for the next several years, given that there is a standout player available who is worthy of the pick.
I think linebacker is the position on defense that is least likely to go in the top 5, or even top 10 for that matter.