Fret not, the Nexus 6P is still in stock on Google Store
Google Store Canada was indeed out of Nexus 6P units, regardless of variant, but only temporarily. As for Google Store US, the stock shortage seems to have been even more short-lived.
With two new HTC-made Nexus phones expected to be released soon, the Nexus 6P (and the Nexus 5X, which was launched last year alongside it) may indeed disappear from Google Store at some point. However, this probably won't happen in the very near future, as the next-gen Nexus handsets might still be a couple of months away. Plus, we'd expect both the Nexus 6P and Nexus 5X to be sold by Google for at least 1 year - thus until this October (since they hit shelves in the second half of October 2015).
We can't say we'd recommend purchasing a Nexus 6P right now, as a couple of new Google smartphones are just around the corner. But, hey, at least you can buy one, if you really want to.
source: Google Store