Well, if we consider AMD's numbers of XBO and PS4's shipped, coupled with MS's shipments, it looks like the 360 is ~1.5M undertracked here, possibly more. More than likely the PS3 is undertracked by a similar amount. This not only means that the gap is actually less than 15M, probably around 14M, but that the PS3 is also performing a little better than VGC suggests.
Having said that, I still don't think it will pull it off UNLESS Sony drops the PS3's price this year to $199 for a 500GB SKU and $149 for the 12GB SKU.