http://www.theverge.com/2012/4/12/2943015/sony-strategy-meeting
The Playstation brand has, overall, been profitable for Sony. The same can't be said for other areas of the company. They will continue to invest in areas that are most profitable, and this includes gaming. Sony has clearly outlined their main product focuses, so you can expect the PS4 to release at a time that gives them the best chance against the competition. Do you really think that Sony would risk releasing their next console 2 years after the Wii U, and 1 year after Microsoft again? They've also said in the past that they won't be last to the market versus Microsoft, and all signs point to a 2013 release.
Sony doesn't have to release the PS4 at a huge loss, and we have no reason to believe that they haven't learned from the mistakes of the PS3. From what I understand, the Vita was approximately sold 'at cost', and it's possible to do the same for their next home console. Even if it's at a slight loss, the entire Playstation brand can recoup that money through software, digital distribution, etc.
With a slimmer, cheaper PS3, Sony will be able to continue selling this console for profit for a potentially longer period of time than even the PS2. #2 is still selling, incredibly, so imagine an even longer life cycle. This strategy is to shore up the PS3 to sell for the indefinite future. The PS4 will offer things unique to the PS3 that people can only get with the 'latest and greatest'. This will have no effect on sales, and the PS3 and PS4 can sell side-by-side for some time without stealing market share from each other.
If the PS4 doesn't come out in 2013, the Playstation brand will likely lose favor with the general consumer audience. Timing has too much to do with the success of such a big brand. If Sony waits until 2014 or later, then they're pretty much done. I just don't see that happening.
