Truthfully, any potential RV park owner that is worried about people staying at the Walmart is worrying about the wrong thing. Those Wally dockers are not now, or ever going to be, a customer for that RV park. They are no more of a threat to that park's business than a Chuck E Cheese is a threat to a 5 star restaurant. Totally different customers.
The big hurdles to building a park are financial and regulatory. It takes a special person (sometimes I think an idiotic one) to pump out 100s of thousands of dollars while pounding their heads against the wall that is government all to build a business the public thinks is undesirable. This is why the resale market for RV parks is exceptionally strong and the new build business is essentially non existent.