Google is endlessly iterating their core service applications - mapping, navigation, voice recognition, gmail, places, and so on. With Chrome they are quite welcomely decoupling the browser (long overdue), though that is one of the only major dependencies on ICS.

The notion that the operating system needs to iterate for Google to move the base forward is not accurate.

Which is interesting seeing the focus on ICS, which makes me wonder whether we're past the point of diminishing returns. People desperately wanted each of the prior iterations because they fixed fundamental flaws in the operating system (e.g. slow runtimes, bloat, etc). From Gingerbread to ICS, however, is largely a "meh" affair on smartphones. Of course new devices come with it, but for the existing base it just isn't that compelling.