There wasn't anything big released July right? If the PS4 is down from last year (likely) and the XB1 up (likely), I can see the XB1 outselling it by a small amount.
Regardless, I expect the gap between the two to be within 20k.
Why would you think that?
While it has been trending slightly below last year in certain months, the continued sell of the Batman bundle which jolted sales up above last year's trend for June considerably should keep it above the line this month as well.
You also have to remember that in the early months this year where PS4 was trending below last year--In those months last year (2014) PS4 was still selling out, and it did not have that momentum going into 2015--by June/July 2014, however, the PS4's sales finally slowed down, and demand was well met, so the PS4 has a much better chance of topping it's numbers from last year for every month in the second have of this year other than September (where it did crazy numbers last year thanks to Destiny).
The batman bundle would still have momentum into July.
I think XB1 will win August.
While it is still a bit early, I think that could be very likely. When you consider things such as the BB deal which has done very well so far, and the two games along with two bundles coming out this month...I think the PS4 will still sell very strong this month, but the X1 could very well out do it.
Yeah, XB1 is going to outsell a battlefront bundle and that COD marketing.
I will say that I think both consoles will do very well this Holiday....the November thread will be quite entertaining to watch

In any case, I think that if Sony can come out with a $350 Star Wars bundle for the whole month (well I guess it would only be two weeks since it launches on the 17th), then they could very well take the month regardless of what Microsoft does with the X1 deals.
But either way I think that it will be a lot closer than the blow out we saw last year thanks to Sony actually having some good marketing deals this time around.