It's not worth arguing about....everything will be fine. Just make sure that there are no underlying medical/emotional conditions and let time do the work.
Search online for a 1997 study by Warren P. Silberstein, M.D. According to him, 1/4 -1/3 of children still wet their beds at age 4. Every year thereafter, 15% will stop naturally. His article discusses treatments.
My anecdotal experience is that my friends with the "string-bean" skinny kids have a tendency to wet the bed longer that "thicker kids." I had a family member told that her daughter's body just wasn't prepared to hold it through the night yet.