Well, yes that was Albo's folly right there. As soon as Dutton withdrew support, he should not have pushed ahead.
My hypothetical about 1967 would have to assume that the referendum was proposed by the government and opposed by the opposition party. As you say, that didn't happen.
Having said all that, I do think it's feasible that in the modern era, with social media influence being as it is, both major parties could support a constitutional change and it could still be defeated. All it would take is a populist snake oil salesman with deep pockets and a willingness to play to the fears and base instincts of the voters.
I doubt we will see another Referendum on anything for another 30 years if that.