Well im bi and i had to come out , i think its necessary to be honest. Its even more complicated than being gay in some areas e.g. being in a relationship with a girl and she doesnt trust you because youre attracted to both sexes. It can get very complicated
I guess it's up to you. I think you should because if you decide to get with someone of the same sex it could still come as a massive shock to the people around you, regardless of whether or not you are still attracted to the other sex.
They'll have almost the same reaction because at the end you like ppl from your same genre but I guess they can tolerate or deal with it easier than if you're gay. You only need to be feel ready to come out.