In college, our coach made all of the sprinters run a mile time trial twice during the fall. Once right when fall training started, and once in the middle of December, right before we left for winter break.
Some of the male sprinters would be as slow as 6 minutes, but 4 or 5 would always break 5. Our fastest 100m guy was only a 10.4 runner, but he broke 5 minutes in that time trial. Another guy ran 10.6, but could only run 5:50. It didn't seem there was really a correlation between their ability to run the mile and their 100m time (as most of us would expect).
So my point is, I see no reason why we should be confident that Bolt would be faster or slower than that 10.4 guy was in the mile. I think if you took the top 10 100m runners in the world and offered them a huge prize to break 5:00, at least 2 or 3 of them would do it. I think it would be hard to predict which would be able to do it and which wouldn't.
Is it possible that Bolt would go out and only manage 6 minutes? Of course. But I sure wouldn't bet for or against him, since it is basically a roll of the dice. Ultimately, if the discussion is "Can Bolt break 5," the answer has to be "unlikely, but there is a possibility." If the question is "can the best 100m sprinters in the world break 5," the answer clearly (to me) is "Of course a few of them can."