Guys, every character with a cover story returns to the main narrative. Enel went to the Moon, perhaps acquiring knowledge from the Void Century, and also possesses the best Logia in the series. To be consistent, Enel must know of Imu's existence and is waiting for the right moment to attack. Remember that to this day in the series, no character has Observation Haki with a better range than Enel's. It's just a guess, with a low probability of happening, anyway.