The internet exploded when trainers started claiming they found legendary Pokémon in the game. Many claimed this was fake, some thought it was real, but ultimately Niantic responded by revoking these Pokémon from the users accounts according to ign:
“We recently noticed that a few Legendary Pokemon got into a few accounts when they shouldn’t have, To preserve the game’s integrity and as a measure of fairness, we have rectified the situation and revoked the legendary Pokemon from the Trainers’ accounts.”
While trainers wait patiently for Niantic to release their legendary Pokémon, the game will start to hit a plateau as more and more users feel that their is not enough end-game content. Niantic will have to get it together and start releasing more content in order to keep this game going.