Walking away does Canada no good and gives the Yanks a good excuse to abrogate the treaty.  Pushing talks into 2018, as far as possible, starts to make it an election issue, particularly in US border states. Members of Congress there have a much clearer picture of how important NAFTA is to the US.  Even if The Donald says he will rip up the treaty, Congress may not let him, and they have the final say.
I predict there will be some give on Canada's part on auto parts country of origin rules. Not 50%, but certainly more American-made components. Also a slight opening in the supply-management rules so that there will be a quota of US-sourced dairy, eggs, and poultry. I believe this was done in CETA for dairy. But no give on dispute settlement or procurement.
Softwood lumber will have to wait again.  This disagreement would go away if we agreed to ship raw logs, but the finishing is where the $$$ is. No deal.