Modern PT wood chemicals are highly corrosive to aluminum (and some other metals, but particularly aluminum), which is used a good bit in RV construction. It would not be nice to have your outside siding dissolve away in a couple of years.
I don't know that house wrap would help things much; the usual route for water intrusion is not through the side of the wall, but through openings and seams where the hose wrap wouldn't seal. It might help to keep any moisture that got in within the shell of the RV, which would be a detriment.