Analyst: PS4 and Xbox One Will Ship 6 Million Units Before the Year's End.

[Slimebeast]

Until December 31 sales should go:

PS4: 4 million
Xbone 2.5 million

First half of 2014 weekly sales will be rufly like this:

PS4 115,000 per week
(USA 45K, Europe 40K, Japan & rest 30K)

Xbone 50,000 per week
(USA 30K, Europe 15K, Japan & rest 5K)

So install base by mid 2014 should be:
PS4: +7 million
Xbone: 4 million

Sales by end of 2014 are much harder to perdict since Xbone will be forced to make a desperate price cut in September 2014, but it's hard to estimate its effects at this point.