Plus ignoring the Switch, there is also the Scorpio this holiday season. As you said, the PS4's competition the last holiday for example was a dead console (The Wii U) and a inferior identical console (One/S). Really anyone looking to purchase a new gaming system shoudl have looked at the PS4/Pro.

This upcoming season though, there is the new hot item, the Switch. Which is vastly different than the PS4/Pro and its offerings. Then there is the new Scorpio, which even if it is essentially identical to the PS4 in its offereings, it will be the top end model. No longer the inferior console when talking multiplats.

Both should steal a console or two from the PS4 this holiday season. So expecting same sales from PS4 this year as last year is being dillusional. One has to admit compared to last year, the PS4 has competition this year. It's like last year they were the Warriors palying the worst teams in the NBA. This year, they are playing the best teams in the NBA. Now I'm not saying the warriors can't still win, or won't, just that they won't be blow outs this year. The other teams will score more points and the warriors will score less points. 

One thing to point out is I think a big reason Microsoft sucked this generation has more to do with the XBox One initially focusing on Kinect and DRM. Microsoft changed this not long after, but the damage was done. Consoles get branded fast and XBone stuck. I don't think most consumers care about the power between PS4 and XBox One. Its mostly fanboy bragging rights. 

It's also hard to pinpoint Microsoft. Sony and Nintendo seem dedicated to this market, but Microsoft was only around to stop Sony. So how the Scorpio will affect the PS4 is harder to gauge because we don't know what direction Microsoft is taken. That said, I agree that Scorpio does bring Sony some competition. Consumers who haven't entered Gen 8 now have more choices than they did in 2013.

7 million for PS4 already, the strongest start of the year it's had. Looks like this could very well be the PS4's best year, which I've been saying for a while. Will be hard for Switch to post a 17m+ 2017.

I am shocked that Nintendo Switch is selling so well. I believe that Zelda plus awesome marking is making the switch sell like hotcakes

PS4 no question.

Well, so far the Switch managed above 200K a week. This probably means around 20K win against the PS4 per week. In 50 weeks the million is made. As holidays are insane, I declare it will be very close. Or Switch sales drop below 200K. In which case PS4 will win.

And to your addendum, that Switch is only available since may: keep in mind that launch moves a lot of units, but it will niot have another launch. So ongoing momentum is relevant here.

Someone has to remember to necro bump this in 2018.

It's going to be the Switch, that's what the data indicates,

As of the end of April after 8 week of Switch sales, and 17 weeks of PS4:
PS4 4,234,849
NS 3,488,881

Switch is outselling the PS4 on average per week, despite the current supply constraint. It's quickly closed the gap to 750K, and Switch will have the bigger summer, surpassing PS4 for the year during that time.

Typically, Nintendo benefits more from holiday season sales than other companies, and they're targeting 18 million consoles to be produced this year, and this number has risen twice already in the last 3 months, and could rise again over the next 6. More so this year considering PS4 doesn't have as exciting a holiday this year as last year. So, in other words, the holidays, rather than affording PS4 the opportunity to catch up, will most likely extend Switch's lead considerably.

Wow, you judge the Switch low. So far supply defines Switch sales, and that was always above 200K. So it seems there is ongoing demand for 200K at least at the moment. Dropping below 100K seems a lot given this.

VGC figures are wrong, we've got official figures from Sony now.

7 million sold this year as of June 11th.