No doubt he'll be a first-ballot Hall of Famer (once the voters are convinced he's retired, at least), but I don't believe he deserves it. He never won a playoff game without BB coaching his defense. I usually don't give creedence to the whole "never did anything without so-and-so" argument, but in this case the evidence is overwhelming. All of Parcells' successful teams were all about the defense and BB had a lot of autonomy. You hear stories about how Parcells was clueless about a defensive game plan and basically told BB "it better work". The '96 Patriots team is a great example, the offense was actually quite weak down the stretch, but BB's late-season defense carried them.
The media loves his persona, but I don't believe an objective evaluation can put him in the class of "great" coaches.