I wouldn't come out unless I was 90% sure I am going transition as soon as I say it. Your close to living half your good years in life (counting all the good years as below 80), do you want the rest of the other years to be the same?
What will happen the sun becomes purple, and the solar system is eaten by a big dark hole like pacman, each planet look like a bowling ball into the hole.
I would do real life experience for a while, and tell people who are strangers you are a man... first break the ice, and then go based on that.
We weren't born with a how-to-live-life manual when we were born, and there's no rule that you can't be a man. If people don't like it, forget about until they come to terms with it.