I don't think I'm alone in saying I'm sad about Michael Gambon's passing. He was one of many incredible British actors to lend their talents to the adult characters in the Harry Potter series, and he had a tough act to follow. Richard Harris perfectly portrayed Dumbledore's sensitive and soft-spoken nature in the first two movies, perhaps when it was needed most. After he died in 2002, Gambon jumped right into the role and made it his own. Even though fans didn't always like his creative choices that weren't necessarily book-accurate (HARRY, DID YOU PUT YOUR NAME IN THE GOBLET OF FIRE), he gave Dumbledore an energy level that Harris couldn't muster.
I don't know who could play Dumbledore in the upcoming limited series based on the seven books. I don't envy them for having to follow the three incredible actors who've played this iconic character. If you are shaking in anticipation for said series, I hope these Harry Potter memes can tide you over for the time being.