Destiny Bundle will do it.

But it will lose that during the Halo Collection over the Holiday.

Not necessary, Sony could get a Gta V Bundle , that + the traditionnal assasassin's creed bundle + natural PS4 popularity everywhere, especially outside america where One popularity is weak( even in Japan, without relevant games, christmas will sell PS4) , i dont think Halo Collection would be enough to sell more One than PS4 during christmas, except the first week maybe.

My feeling is that Halo will boost XBO sales but because I think that most early adopters are the hardcore Xbox users who would already be Halo buyers, that it wont have as much affect as one would expect.

September it will double it

September is too optimistic, impossible, unless...TLOU remaster offers a big boost. In september, One will reach 5M, so PS4 should reach +1,7M to reach the double, that is impossible, July and august are always poor sales period.

A couple of weeks after TLOU re-release, so before the september equinox is my guess.

2014 sales are 3 to 1 ps4 to xb1 overall, and in recent months that's trending upwards.

Black Friday 2014! Mark my words!

September, with the release of the Destiny bundle.

before 2015, probably between the Black Friday and end of the year.

Below is a NON-LINEAR REGRESSION ESTIMATE

The regression (estimate) above tells us that the PS4/XB1 ratio will hit 1.9 by the end of the year, and therefore 2015 is the year when PS4 will actually double the XB1. However, that simple analysis above fails to take into account two facts:

a) Black Friday-Christmas period (and generally the last quarter) is a very fast paced period, which will accelerate the process.

b) The new XB1 policies, pricing, and exclusives are likely to give XB1 a boost in some territories, probably reversing the scenario.

The net effect is not clear. As per my original predictions, the PS4 will be close to 2x XB1 at the end of this year, if not already above it. In either case, september is technically too optimistic. This is funny because a LINEAR (and technically wrong) estimate makes exactly the same estimate of doubling (September 20th to be specific). This shows the "optimism bias" in people's minds (at least ps4 supporters) and also how the wrong application of science may mislead people.