How do you know it would end the friendship? There had to be a close bond there if he wanted the guy for his best man at the wedding. Saying, hey, "I've had a crush on you forever, she's a lucky lady, and I'll shave her head if she ever hurts you.." or something along those lines. But on the other hand, there is no point at this time FOR him to say anything - he missed his chance. It should have happened when the feelings became a stronger/unbearable.
I realize not everyone is as outspoken or brazen as I am (understatement of the century?) *Glares at anyone who even THINKS about commenting on that*
But if something is eating away at you, you need to say something or it gets worse. It would be inappropriate, I think, for him to say anything about it now. Maybe 10 or so years down the road when the hilarity of it might arise from the entire situation.