I didn't ask other people to use correct pronouns until I had taken steps to fully come out: ie name change, gender marker on DL, started T. Up until then, it felt silly to me, because clearly, externally, I was still F to everyone else. And even then, after all that time, it still felt like family, friends, and coworkers were just humoring me, like I was a loony or something. Now, finally, it seems very normal, after 19 months on T.
So ask him what he would prefer, and what timeline. More important for you to show interest and concern, rather than just assume and be wrong.
Jay