The only thing we have regarding sales are some relative numbers for the original core trio of books regarding initial print runs. There has been a deafening silence on sales of books released after that point.
We're all going to read into that void as we see fit, and without numbers that neither of us have access to, neither my skepticism nor others fanboyism is going to bend much. I swear, some folks seem to take personal offense at the very suggestion that the 4e might not be the most financially successful edition of all time by any metric possible.