The PS4 sells well when there are popular 3rd party titles also selling. The PS4's higher price hurts them when that isn't the case. There are enough big titles coming out at the end of the year that keeping the $399 price could work.
However, I expect Microsoft to make another strong push on price/value for the holidays. If the XB1 gets close to a $299 price or equivalent that would be enough to break the PS4's momentum if it is still stuck at $399. Keeping that momentum alone is probably worth a price cut due to the marketing advantage it gives them. Sony has a chance to cross a tipping point where its market share alone would be a huge benefit to the PS4. It'll become the default console to buy and have first crack at any exclusive deals.
I think another reason why Sony might lower the price of the PS4 is that Project Morpheus is coming out next year. The more consoles they sell, the easier it will be to sell the VR addon. Therefore it makes sense to sell as many consoles this holiday season as possible before the Morpheus debut in the first half of 2016.
Even without strong titles from third parties, Sony still won four out of the first five months this year. Their brand is strong except for Vita and even that could be strong but they simply didn't market it like they should have and releasing PSTV killed any chance of Vita having an HDMI port.
Back to PS4, Sony could easily rival Xbox One at $300 this holiday season by having a few different bundles at $400. COD and Battlefront limited edition at $400 plus a Sony "exclusives" bundle at $400 which would include their exclusives released thus far via digital download.
I agree in regards to lowering the price due to Morpheus but that's more about when Morpheus gets released. I'm still guessing September 2016. Early 2016 would take away the focus from Uncharted 4 and SFV and cause consumers to spend more money at once as opposed to September being a slower month for them and the main focus being Morpheus. Also, there has to be games, good games for Morpheus at launch and the price can't be that expensive or it's going to bomb once the novelty wares off.
U.S. wise, I think that it will always be close. I don't see Sony gaining lead of more than 1m if that and if Microsoft was to surpass them, I don't see them going past a 1m lead. It's just too close for either to gain a big lead. One of them would have to screw up real bad in order for that to happen. Rest of the world though, it's already over.
My prediction still remains the same - Sony drops the price of the PS4 to $300 at E3 2016 and announces a $200 price tag for Morpheus. Unless Xbox One blows away PS4 in sales the next three months, I don't see Sony lowering the price at all this year.