If he is getting a multi-parametric mri, he will get a pirad score. My score was 5, meaning clinically significant cancer was highly likely to be found upon biopsy. So, don't forget to ask for his pirad score when he gets his mri results.
Other than that, it's a waiting game and you just have to be patient. Strangely, I found knowing what I had to deal with better than not knowing, so I was glad when my diagnosis was confirmed and then I could at least get on with dealing with it.
Members of this forum will help to clarify things for you if he needs treatment. And don't forget the specialist nurses from PCUK - call them - they're brilliant.