I believe that Ryan Dancey was tossing that number around with regard to 3.X, though we might not have heard about it until later. That said, I'm leery of saying that this proves anything about 5E, because the point in question was that 3.5 wasn't necessarily producing too many books to survive. That 5E is doing better is dependent on a lot of factors, but the pace of overall releases has yet to be shown to be one of them; at best, people seem to be trying to draw inferences regarding sales volume, but even that's tricky, because why those volumes are what they are is almost completely speculative.