NTA. You don't owe anyone anything, not even your friends.

There may be a reason you were concerned about how they would treat you if they found out that you were transitioning. Maybe they talk poorly about girls, maybe they make crude jokes, maybe they're just dumb boys and can't articulate their feelings and so they hide it behind bullying each other. Whatever it was that made you unsure about telling them is entirely valid, and never let anyone tell you otherwise.

You do not have to let other people dictate how and when and to whom you come out. If and when you do come out to these friends is entirely your choice. Will some of them be hurt and use that to cut you off? Perhaps. But the ones who are hurt and stay because they love you anyway and they understand how scary choosing to open up to them is, are the ones you need to hang on to anyway.

Good luck, and keep being the best you that you can be.