there is no reason to rush it. even if it does not drop, you should wait til he is fully grown to neuter him. (1.5-2 yrs). The issue with the retained testicle becoming metastatic is something that happens when the dog is older (if he is not neutered).
I agree, there is no rush. Your boy deserves the benefits of the hormones for proper growth and development, both primary and secondary. It can still drop, too. Actually, if the undescended testicle bothers you, that one can be searched for by ultrasound to make sure it is not stuck in the abdominal cavity and at the most, that being the case, remove the one.
When Ringer's testicle didn't drop, his co-ower had me go to a lot of different vets here in Florida including a specialist. They all agreed that I could wait until he was between 18 to 24 months to have it removed without worrying about it becoming cancerous.