Soon, you and your Pokémon will be able to go against Pokémon Go trainers worldwide through the newly announced Go Battle League system.
Niantic introduced Trainer Battles last year to allow players to fight other nearby trainers and their friends even if they aren’t near if they are in your Ultra or Best Friends lists. The Go Battle League system will have you fighting random trainers all around the world.
The details of the new system are still unknown, but Niantic did promise to share more in a video which will be coming soon. The only thing we know for now is that "trainers will be able to walk in order to earn entry" to the Go Battle League, and that it is a ranked system.