So, yes, you can buy a device with stock android. It just has to be a google phone, not a 3rd party for the most part.
Except now, two issues: 1) More a quibble, but I'd say that people around here pushing AOSP makes the term "stock Android" a bit less clear.
2) Article claims the new Pixels will have some other variant of Android, based on current stock Nougat but with additional support baked in for things like their new VR headset and Google Assistant.
Which strengthens FuzzyZeus' point: determining which version of Android a given phone comes with (and which it can support, both now and in the future) is an extremely muddled game, with the OEMs and now Google itself not doing anyone any favors.
It just might not be as good, because its not controlled by google. But, I do think that argument died a long a time ago because of the cruft OEM's have been adding to android and the common refusal to upgrade phones (though that has been getting better lately).
Is this strictly true if google bakes their apps in (play music etc.)