Are you waiting for that "aha!" moment to finally figure out your special role on the world's stage?
Do you expect that one day your specialty will just hit you like a bolt of lightning?
If you're waiting for the light bulb to turn on, you may end up sitting in the dark for a very long time. More often than not, identifying your niche and your specialty is more like a silhouette emerging through the fog.
In my own experience, picking a niche always comes about gradually. You're working on one thing, and then another thing similar to that, and before long, you are being associated with a specific specialty or setting.