PS4's ownership of the market is going to grow massively next year, 20-25 million is what it will sell IMO, 3rd party sales will shift even more in Sony's favor for new console buyers, the line-up of exclusives for PS4 is very strong in 2015.
At best Xbox One's hardware sales level off with the small line-up of exclusives coming next year, the true exclusives currently lined up for the second half of 2015 will at best garner similar numbers to this year, so about 7 million Xbox One's will be sold in 2015.
If MS can get more exclusives like Scalebound, Crackdown, Phantom Dust and some others that don't release on PC or 360 then the system will see some growth of sales compared to 2014, at best it'll be about 9 million units sold in 2015.
Wii U will see great growth because it has loads of exclusives coming in 2015, plus it has a big library of games already out, which adds to it's appeal, IMO 5 million is the minimum to expect perhaps 7 million if Nintendo has more surprises to come, they drop the price of the system down $50 and actually market the platform as a new platform to the audience they're targeting.
I think PS4 will have a price drop by $50 at some point in the year, coupled with more of Sony's excellent marketing, Xbox One may stay at it's current price of $349, Microsoft are in the business to make money, not chuck their profits on the fire to try to gain some level of market share when that's impossible and Wii U will drop $50 too.
To some up:
PS4= 20-25Million
XB1= 7-9Million
WiiU= 5-7Million.
