Got he same problem with my lab. when he was about 6 months i took him in for a check up and the young vet told me that he should have an op' to prevent the risk of cancer, with him being so young i really didnt want him to go through that and decided to ask again at his 1 year booster.
This time i got an older vet and he said not to worry about it but keep an eye on him, that he had seen alot more cases of cancer in dogs with both balls dropped and if he did get cancer then it would probably when he was 9 or 10 years plus.