Interestingly, Google is citing the 18-month update policy as the reason why the Galaxy Nexus won't be getting the update. Google's support page says, "Galaxy Nexus, which first launched two years ago, falls outside of the 18-month update window when Google and others traditionally update devices." This makes sense, but it is also annoying given that Android 4.4 is supposed to make older phones run better.
The 18-month update policy has made a bit of difference in the ecosystem, but of course manufacturers and carriers will exploit the loophole in the policy, which is that there is no real timetable as to when the update has to come, just that it has to. Either way, if you have a Galaxy Nexus, you may want to look into grabbing a Nexus 5, before they're all gone.