Check galaxy nexus section. So nexus 7 2012 getting lollipop is a surprise
I don't think it should be a surprise.
Think about it. Specs have improved dramatically over the last 2 years. Also they have become more affordable. While Android OS on the other hand have been made lighter. Apps market is a whole different thing though, cause they on the contrary never seize to grow (due to features additions).
So maybe hardware have increased to a point where it can support for more than 2 versions of Android OS. I think this is a good thing. Maybe Google should update its 18 months policy. But that's for them to decide. All I know is that even if Google stops giving updates to Nexus devices, XDA is now self sustained in the department of ROM development. So even if native upgrade is not provided, likes of Cyanogenmod will still provide ROM's based on newer versions of Android OS.
Case in point: Galaxy Nexus DOES have Android 4.4.4 in the shape of CM 11 on Cyanogenmod. Link: Google Galaxy Nexus (GSM) - maguro Cyanogenmod