Some caveats to push it there:

Price:

$100/Euro/Yen drop in 2015.  19 months represents the longest time a Sony home console price remained unchanged from its launch price (PS2 from October 2000 to May 2002).  For 2015 that would put it at June.

Games:

Pretty much a major first/third party release every month capping with Uncharted in  November and possible FFXV in Japan first.

Adoptability:

More Wii, Xbox 360 users migrating over (pool of 180 million) and PS3 owners making the switch.

Potential Breakdown

North America: 9-11 million?

Europe/Rest of World: 9-11 million?

Japan: 1.5-2 million ?

possibly. in Japan 2015 will be a much better year for PS4 than 2014. and in the west PS4 will be off to a strong start with The Witcher 3, bloodborne, The Order 1886 and Evolve all coming in Q1 and all on just 8th gen and PC or exclusive. it will help a lot. add to that a lot of next years games are going to be just on 8th gen.

there is also a certain price drop to happen, which i expect to be just by 50$, but it will also help sales. and other games like Metal Gear, Batman, Dying Light, Dead Island battlefield, and of course, Uncharted. i think it can happen, but it will be tough, but there is no doubt in my mind that it will be a better year than 2014, which is shapping up to be pretty sold with 5.8 million sold until August. 

Hopefully xbox one sells 10+ million and ps4 20+ million

that way ps4 can have 70% market share.

If the second half of the year is as strong as the first and we won't see delays for major titles, coupled with a price cut which most probably will happen, yeah I think it is definitely possible.

because fuck the WiiU....

I am not sure about how much hardware The Witcher and Evolve will push, since they feel like aimed at PC crowd.

But yea, the rest is set sell a lot of Hardware.

They would only drop the price if Microsoft do it first (yes, removing the Kinect is not a price drop, it appears that $450 and $350 are the sweet prices for the XOne this year), and if that affect PS4 sales, which I think is unlikely.

Japan is a dying market for home console. Even if some few games give some timely boost I can´t see that lasting more than a few weeks, see Mario Kart. Even doubling the baseline it dosen´t effect WW sales that much.

The situation in Europe is strange. Former Wii audience has migrate to tablet and smartphones in NA and Japan (spacially Japan). In the USA, PS4 is traking behind the Wii after only 10 months, even after a inicial launch almost twice as big, however in Europe it´s doing much, much better (if VGChartz is correct).

20 is possible, but I would like to see this year hollydays first.

I feel like the delays of this year kinda strengthens the lineup for 2015 more but you are right, 2013 and 2014 had to represent the years that developers get all the delays out of their system.

Also looking at the schedule for the first two quarters, some months you are looking at 2-3 major titles releasing a month, along with known sellers.

They need to, if they ship only 10 - 15 million a year it will sell less than the original PS1.