My only advice would be not to let it change anything between the two of you, which it sounds like it won't, and if any of the rest of your group of friends have a problem with it then give them a piece of your mind.
It's 2014.
yep 2014, unless he has great anecdotes that are really funny about embarrassing situations, then it's of no interest really
Mate of mine is gay, he came out about 5 years after we'd all worked it out for ourselves, and told us by phone whilst he was away in Australia. He'd been keeping quiet in case we didn't like it - which was odd because I'd have thought the 5 years of constant gay innuendo followed by PC discussion on how in reality it would be fine was sufficient clue we'd worked it out.
I sometimes think we may actually have known before he did.
His nickname is Sweety ffs.