I'm not sure there is such a clear-cut correlation.

A certain segment of the "car-free" is made up of people who don't really want to be car-free, but are out on bikes due to lack of money, DUI arrests, etc. Probably not a big segment, but I would guess that very few of those folks have any burning interest in vacation travel on bikes.

Other car-free living folk are those who have chosen to live in dense areas, close to their places of work and business (or have found themselves living in such areas, and have realized how much quicker/more pleasant it can be to get to work/business by bike instead of by car.) A subset of these mostly short-trip-taking cyclists will be interested in longer self-contained touring, but I'm guessing that it's pretty unlikely that there is a 1-to-1 correlation.

The guy or girl who lives out in the (relative) boonies, regularly racking up 40-mile days of bike commuting/shopping, is probably the most likely car-free-to-bike-tourist crossover (although maybe on their vacations, they would prefer to lie in a hammock all day with a nice umbrella drink ) but I would bet that they are the rarest of car-free folk.

I think the basic point is that you're talking about a sliver of a sliver of a sliver of the population. How many (somewhat) dedicated cyclists in the U.S.? Of those, how many are interested in touring? And of those, how many are interested in self-contained bike camping (as opposed to doing organized tours, and/or staying in hotels along the way?)