Hitler certainly had more of an impact on the world than Elvis, so I think he will be remembered (I hesitate to use the word "live") longer.
No he won't be forgotten. The severity of what he did may be lost to time though, due to people who think Hitler is anyone and anything they dislike, or people who romanticize him.
I hope Hitler is never forgotten. If we forget him we forget his heinous actions. "Those who cannot remember the past are condemned to repeat it."
no one remembers Mother Teresa , no one speaks of her, they only pick the negatives of what she may have done ( using used syringes) even tho she gave up her life for others, no one recognises her for that