Even if they COULD muster those 67 votes, see my above. SCOTUS has ruled several times that treaties cannot supersede the Constitution.
Further, those 67 votes are a HARD 67, iterated in the Constitution. This is not the more flexible Filibuster Rule, which CAN be changed at the start of each Senate.
I agree that it is never going to happen, but should point out that the Treaty Clause in the Constitution (Article II, Section 2, Clause 2) does not necessarily require 67 Senators to ratify, just "two-thirds of the Senators present" for the vote. Theoretically, 50 democrat Senators could ratify if at least 25 Republicans don't show up for the vote.