According to Taiwan's Digitimes, sources at the PS4's component makers are saying the plan is to begin shipping the PS4 this August, so it can arrive in stores by the end of the year.
Foxconn and Pegatron Technology will apparently assemble the console for Sony, and the goal is to have an annual shipment of 16 million units. That's... a lot! It such a high number that, quite honestly, I'm not entirely sure I believe it.
That isn't to say I don't think the PS4 will be a hit, but rather, I just don't see Sony flooding the market with sixteen million consoles at the end of this year. Maybe the sources refer to the financial year—which would end in the spring. That makes a little more sense. I guess.
For more on Digitimes, and the accuracy of their rumors, check out this Time article.
Kotaku is following up with Sony and will update this post should the company comment.

http://kotaku.com/5988839/rumor-sony...-for-this-year