Dogs run on because of their hunting instinct not their balls! Whoever takes him on knows they cant breed from him so why would it be an issue in 5yrs time? My mam used to say, If tha's nowt nice to say keep the gob shut young un.
Looks a trim, healthy dog. I would love to take him on but I have 2 terriors and a lab at the min so I dont think I could give another dog enough time. Its not an easy descision giving up a dog, best of luck with the sale Polkey. Sorry cant help you at the min.