I think Niantic could introduce PvE

PvE could be implemented to introduce a storyline into the game like the main series, and events can be triggered by walking a certain amount of distance(walking 10km to continue the story) or being near certain areas like a waterbody (like the lake of rage story in johto). Also, virtual buildings for the storyline could be spawned ingame for the player to interact with (like the Silph Co building) to fight Team Rocket, and gyms with gym leaders can spawn, and the player can fight the gym to unlock rewards and badges. Maybe for boss battles, Niantic could implement AI that can dodge of varying difficulties that can rival the player's dodging skill. Maybe PvE can be a way to obtain rare items from missions and master balls as well. Npcs like bug handlers or the magikarp salesman (200 coins to get a perfect magikarp maybe?)can spawn to add extra fun into the game.