Every time someone asks if a specific model will be available, the answer is always the same, which boils down to this:
As long as it is not displayed on the web site (in the phone selection page), either no one knows or no one is allowed to say it.
So you will never get a straight "yes" answer, unless it is already in the phone selection page, in which case you wouldn't need to ask the question.
You also will never get a straight "no" answer either, because even if the moderators know that this model is not expected to ever be available, the people in charge could decide to make it available down the road. And if you could get a straight "no", it would be a clue that "we don't know" equals either "we're looking into it" or "yes".
Finally, had you scrolled down, you would have spotted a thread named "Nexus 5X / Nexus 6P", where that exact same question has already been asked and answered.
Rogers had only the 6P in their reserve system up to not long ago - it now appears to be available. Telus says "coming November 4, 2015" for the 6P. No mention of the 5X. None of the budget subsidiaries list it (Fido, Koodo, Virgin). Wind has both Nexus listed as "coming soon" without more details.
That said, I suggest a bit of math. Compare the monthly cost with the $350 rebate vs the BYOD cost (for the same plan). Here in Québec that's a $15 difference. Multiply that $15 by 24 months and you'll find out that you'll be paying $360 to get that initial $350 rebate. So after 2 years, you'll have actually paid $10 more by subsidizing the phone rather than paying it at full price from Google.
Nexus phones appear to receive the updates for almost 3 years after their release (the Nexus 4, released 3 years ago, won't be getting Marshmallow, but my Nexus 5 is currently running Marshmallow), so you could keep your Nexus device 3 years rather than 2, which will make purchase at full price cost even less in the long run. Plus you can switch to a better plan at any time, or another carrier.