Unlikely in a 13 year old trailer, unless it has been grossly neglected. In a 30 or 40 year old unit, it would be more likely. It's all about maintenance.
The fact that the wood is exposed underneath is not the issue. Scamp
coats the underside with fiberglass resin. Almost all floor rot comes from above: neglected leaks
, vents, plumbing, and, to a much lesser extent, rivets.
But it always makes sense to check. Pay special attention around the outer edges under windows
and inside cabinets. If there is a shower, feel for softness, and inspect underneath.