I wonder if the ?'n mark at the end is his get-out clause in the unlikely event (ahem) of prediction failure?
Next year we could have 3x6+1 (false prophet) = 19, and the year after that it could be 3x6+1 (false prophet) +1 (beast) = 20. And the year after that you could always add your partridge in a pear tree, right?
OK, maybe not, but who's brave enough to give me any odds that there won't be such a prediction for every year up to 2025 at least?