Sealing the floor when new might block some out the outasing of bothe the new carpet and new partical board floor. After that I don't see an issue. If its sealed the moisture will not get in it in the first place.

Make sure to pick a time when the floor has completly dried and humidity is low so it has as little moisture in it as possible.
We just replaced the floors in our coach and we used and epoxy wood sealer like that used on wood boats. We did it before the wood was even installed. Where we cut it down to the correct width we then redressed to keep it sealed.
We used a pretty good quality of wood and once it was sealed it had a very nice honey color to it. It was almost a shame to cover it up but with all the elevator bolts it looked a little odd. Once bolted down we did a final top coat to try to seal around the bolts. Then we installed a solid sheet vinyl flooring before the body was set back on the floor. That made sure all the storage areas have nice clean floors as well.
Our attempt was to prevent water from ever getting a chance to make direct contact with the floor ever again. In a camper its not a question if it will leak as much as a question of when it will leak. So we took extensive preventative measures.
In a couple years we may do a thin laminate pre finished floor in just the visable areas. Most coaches will only take 2 boxes at most to do the visable areas. If using the thin floor it's only about 70-80lb of total weight at most and it is spread evenly through the coach.