They are just updates, when you look when the i series was first introduced which was Nehalem (which was the start of the i-series chip)(currently on the Sandy Bridge - Ivy Bridge) it coincided with the release of Windows 7 well, maybe it was a few months after Windows 7 was released.
Intel also have a release schedule similar to Apple's phone series. Their first chip of the series is usually called the Tock and the followup will be the Tick. In which the Tock has a new architecture and the Tick with a die shrink. Ivy Bridge was the Tick.
But if you look at the next major change based on Intel Developer Conference notes 2011, you will see that the Haswell which is the next generation of cores, are due to be release after Windows 8 launch. Sure they haven't finalized the chip's name, but they will have a new chip by the time Windows 8 comes out.
http://en.wikipedia.org/wiki/Intel_Tick-Tock#Roadmap