The people who voted libertarian in 80 were not disaffected conservatives. They were disenchanted liberals of the New Politics mode. The growth of a conservative oriented libertarianism is an artifact of the Reagan era. Beyond Goldwater's disastrous campaign, they weren't a major force in American politics.
Yeah, but conservatives of the fiscal variety kept cropping up, no matter what was thrown at them. During the height of the New Deal, there was Robert Taft. During the Great Society, there was Goldwater and Reagan. Hubert Humphrey's new policies are not going to make this tendency go away forever.
The worst it could realistically get is another time period like between 1900 and 1920, between the era of the Bourbon Democrats and the proto-libertarian Republicans, where all major modes of political thought were different shades and degrees of liberalism (see the four major candidates in the 1912 election). Eventually, though, it's going to come back.