According to Sony Computer Entertainment president and group CEO, Kaz Hirai, Sony isn't even thinking about the PlayStation 4 yet, because the PlayStation 3 isn't even half-way through its life-cycle yet.
The quote comes from an interview with PC Impress Watch, which was translated by Eurogamer. He said:
"I think the value of the PS3 will continue to rise. Because of this, a near-future PS4 or next-generation home console is not something that we are even debating now. That is to say, we are still concentrating fully upon the PS3."
It's actually quite scary to think that the PlayStation 3 still isn't even 5 years old, but it's good to know Sony will stick to their guns and see our the product's 10-year life-cycle. Or even further, if the PS2 is anything to go by.