18m is 100% certain at this point.
15m before BF week, 16m after BF week. Then another ~600k+ puts it at 16.6m around the PS Experience in early Dec. Add another ~800k the week after and we're at 17.4m+. The week before Christmas week will be huge with 1m+, which puts PS4 at 18.4m++ and then Christmas week itself should be close to 1m as well, putting PS4 at 19.4m+ with one week remaining of the year, where PS4 should sell around 400k putting it very close to 20m.
Remember to quote me at the end of the year!








