
To OP,
it is best ultimately to have a retained testes removed to prevent future problems - the testes are not designed to be at body temperature and so one retained in the body cavity increases the likeliehood of it becoming cancerous at a later stage.
There is no need to have the normal descended one removed - i.e. no need for full castration should you not wish your dog to develop some of the problems that castration
can cause relating to change in temperament, potential feminisation syndrome, unweildy/wooly coat for eg.
At his age it is unlikely to descend (not impossible, but improbable), however there is no urgency to have it removed - I've had specialist advice on this and recommendation is by ages of around 4+ years before it would be regarded as being a "necessary" procedure. So plenty of time to allow for a larger and slow maturing breed to continue to grow and develop at the optimum rate (that is should you prefer to have complete castration).
HTH, Teri