It has also been reported many times that indeed the PS3 has a ten year release cycle, but so did the PS2
(article here). Just because they release a new machine doesn't mean they stop production of the previous version, and it also doesn't meant that they will wait until the 'ten year' mark to release either. PS2 was first released in 2000 and still in production in early 2011 (and possibly now), a good 5 years after the release of the PS3.
The ten year cycle 'minimum' doesn't mean that is when they will release the next console, just that Sony envisage that is the base lifespan of the console before they consider winding up production of it. Demand will dictate its ultimate lifespan. They would be mad to rest on their laurels until 2016 before releasing a new console but I don't think we will see a PS4 in the next 18 months either.