PS4 is most likely too sell over 20M units, with the amount of exclusives coming this year (particularly Q1, 2 & 3), 3rd party marketing deals for those major releases and overall preference of those games within the market.
PS4 is also highly likely to get a price cut down to $299 this year, a $100 price drop is usually what Sony does with their home consoles as the 1st reduction in official RRP and that is guaranteed to have a huge effect, especially with all of the games coming to the system.
Q4 should have R&C which is a big game, likely a few other games yet to be announced for that period.
Judging by the lack of exclusives until Q4 the majority of new 3rd party system sales will probably be made on PS4, I think XB1 may be level with last year's figures by the end of the year.
As history shows Halo is a game that people buy because they have an XBox, not a game that people buy an XBox for at launch or proceeding it's release, same goes for Forza.
There's a possibility of course that MS can announce more for Q4, but with them already having Halo and Forza I doubt it'll be anything that big from their stable of IPs, they already have a bought semi-exclusive multiplat, I doubt they'd risk more negative press by doing another deal like Tomb Raider.
Perhaps a Banjo or a Conker could be released this year or maybe Scalebound or Crackdown are further along than people think, though I'm not sure how effective they'll be at moving hardware.
I think XB1 will have sold between 7.5M and 8M by the end of the year and I think PS4 will top 20M.
