There's a good deal of dubbing in Singin' in the Rain in regard to Reynolds and Hagen, both vocals and dialogue. However, because the end result is so amusingly appropriate, we just accept it and laugh at it.
I would hope that The Wizard of Oz, Gone With the Wind, Citizen Kane, Casablanca, Singin' in the Rain perhaps a few others that I can't think of right now are so sacrosanct, they will never be remade. I hope I'm right, but you never know. I thought a few years ago the we would see a new film of My Fair Lady, which (like West Side Story I'm cautiously open to) but currently that seems unlikely.