We'll see spikes at every major release for a while, then, when SW and HW bases will be greater, PS3 will have a more regular and stable increase in HW sales. A slim and cheaper version could help a lot, too.
Anyway this time the winner is Wii, it started well since day one, nobody will be able to dethronize it, unless Nintendo decides to give it a very short life, but why on earth they should?