Welcome aboard! The good news is your husband has very little cancer. He will have any and all options available. Take some time to learn all of them, you have time. PCa is a very slow growing cancer.
Yes, the general belief is if you have surgery, if recurrence happens, you can have radiation later. It is harder but not impossible to have surgery after radiation. But, with the stats you have given us so far, whatever you (he) decide, he should be able to beat this thing the first go round.
If you have surgery and remove the prostate, some of the cancer may have escaped the capsule and further treatment may be necessary. Again with his stats, this will probably not happen to your husband.
When my urologist gave me the bad news, he said your life will change from this moment on. It would be a good time for your husband to make some lifestyle changes to prepare for his fight. Eat better, back off the red meat, exercise, etc. Six months before my surgery I was 6' 1" and 224 lbs., 1 month before my surgery I was 200 lbs., 1 week after surgery, I was 193 lbs.
Take a deep breath and relax. You have time! We all know what you both feel like right now. You are not alone any more.
Bill from Florida
Age - 62 now, 61 at time of surgery
Feb. 2012 - PSA 18.5 Biopsy 4/27/12
Positive 10 of 12 cores, Gleason 6 then
Da Vinci Surgery 07/17/12, Dr. Vipul Patel, Celebration Health Hospital
Extraprostatic extension, positive margins, bladder neck involvement,
Gleason 3+4=7, involving 50% of gland, prostate weight 57 g.
Stage pT3a, Lymph node involvement: 0/4 All post-op PSA tests undetectable <0.1