Well, it looks like the prediction has failed, but it came extremely close.
We have these numbers as of September 5:
PS4 25.677
XB1 14.031
Given the shipment numbers and sold through by Sony, (29.3m shipped 09/30 and 30.2m sold through by 11/22), we can make the guess that around september 5th, ps4 was undertracked by around 1.3m.
Unfortunately, we haven't received shipped or sold through numbers from MS for 2 quarters, which kinda sucks because it would've been interesting to see how this prediction panned out. All it would have taken was ~500k less (13.5m) for ps4 to have doubled x1.