RV is dying out. Land is getting expensive everywhere, in Mexico and US. In the US there are national and state parks that will - hopefully - remain open, but in Mexico all land is private, and their population is growing faster too, many children in families.
Yes, good places are usually taken by permanent residents, baby boomers numbers will be growing for another 5-10 years, then it will subside, but by then there will be no RV parks. Besides, it's easier for a park owner to deal with permanent residents than transients.
It is interesting though, that there are fewer RV tourists in Mexico, I noticed this too. Don't know why. Probably recession is to blame. So there is more pressure on the park owner to sell. On waterfront in Baja, everybody that I asked, were approached at some point by some super-mega resort developer, but the owners are old, this is their home, so they are reluctant to go.