Low risk hpv cannot become high risk because they are different virus strains. The strains that cause warts do not cause cancer and vice versa. However, it is possible to carry multiple strains at the same time. But since your wife was negative for high risk and you both remain faithful, you will only have the warts to worry about, not cancer. I suggest checking out some of the forums and articles by Dr. Hunter Handsfield regarding hpv. Very knowledgeable.