That isn't really Google's fault. They have to deal with a bunch of phone manufactures who all like to have their own custom android experience (Touchwiz, sense, etc). Google has released the ICS source code which then allows different manufactures(Samsung, Motorola, HTC, etc) to port these to their devices and update them.
Apple on the other hand is in charge of manufacturing and development so they only have to make iOS run on a handful on devices (iPhones and iPads).
As you can see it is a little easier for able to push their iOS updates when they are in charge of all the steps. Google on the other hand is only responsible for one part of the process and has to rely on manufactures to push these updates to their customers.
Apple does have the advantage over Android in that regard. But it is more of the phone manufactures/carriers faults for being lazy and not pushing updates that are ready to their customers.
Hope that all made sense.
Still iOS = rehashed ICS