From my once off experience of discovering a good friend is gay, your friends relationships will change, because he is moving from hiding something he didn't trust the team to revealing something deeper about his private life. The choice of if it is ultimately a positive or negative change will be up to the individual as long as your friend isn't aggressively defensive but is calmly straightforward about it.
I think the important thing for your friend is to not be defensive, not anticipate everyone is going to freak out, but decide ahead of time to be forgiving and gracious whatever happens - that will win over the most people possible.
As a rather blunt person myself, I would speak about the "elephant in the room" and explicitly say something like "I now trust the team enough that I can be more open about my private life and reveal my choice to have a boyfriend rather than girlfriend".
There isn't a "perfect" way of revealing personal details about yourself that you suspect some will react negatively about, because some people are just not that mature and experienced with life broadly enough to have a good reaction and are instead running on precanned responses from others around them.
When and if the subject comes up, you have as much right to mention your choice of partner as anyone else does, and as much right as anyone else to mention your private life.
If there are particular team mates your friend is certain will support him in this, then talking to them first and somewhere private so they can get through any of their own questions and comments would be helpful (on the basis your friend is anticipating problems)
later you can introduce some humor into the situation, eg if someone complains about the wife / girlfriend being moody during her monthly periods you can laughingly say "sorry to hear that, but very glad I won't ever have that problem!" (or "at least you can mark it on the calendar - I don't get forewarning")
If the comments are getting a unthinking or offensive, you can gently but firmly redirect it, eg for me, as a Christian, when people use Jesus's name in vain, I will sometimes interject in a calm manor "Yes, I know him, do you want an introduction?" - it clearly indicates they are saying something about someone I care about, but also opening the door to discuss Him if they want to.