According to Mcvuk, a trusted source has told them that hardware for the PS4 and Xbox One are up from the prior week, but a price cut combined with strong FIFA sales has pushed the Xbox One ahead for the week. Another report from Mcvuk suggests that FIFA actually sold better on the PS4.
We will find out the real numbers soon enough but MCVUK has a solid track record with UK sales, considering that's pretty much what the site is all about. While the two rumors may seem at odds with each other, they may both be partially true. I could see the Xbox One, with its recent price drop, outselling the PS4 for the week. I could also see FIFA selling better on the PS4 as the install base is bigger. I think the only jump in logic I don't agree with MCVUK about is that FIFA helped push the Xbox One. I would put that on the price drop, personally.
I'm looking forward to seeing the actual numbers and seeing how this plays out going forward. Microsoft still has a long way to go to come back in the UK, but this could be the start of something interesting. Or it could be a price drop bump that goes back down to usual sales numbers after a couple weeks. This holiday in North America and the UK will be pretty interesting. As for the rest of the world... not so much.
UK sales have been interesting. There have been a lot of moves MS have made to boost sales here, from bundling of FIFA at launch to temporary price reductions (TF pack was £350 at quite a few places back in March - when I got mine), and now an official price drop. Sony meanwhile has had bundles adding value as games are released but not felt so much need for bigger gestures. A single week in isolation isn't much particularly as the numbers were still close and a lot of PS4 sales were in the weeks prior for Destiny bundles. I can see from my friends list that there is still a decent number of active 360 players out there and it's MS's job to convert those to X1 players in the future.