N7 2012 has Nvidia, N7 2013 has Qualcomm. Chipsets shouldn't matter for a company of Google's size. They all seem to have ARM tech underneath anyway.
N9 is a poor tablet for the price, probably didn't sell well so its not their priority.
I agree with you that Chipset shouldn't matter. That was my point.
N9 is good for £200 which is what you can get it for. And it's a Nexus, so they have to update it no matter what.