I don't think Mambo should be replaced for the very reason that it IS old. When the English were first building their Latin-American syllabus, I remember reading somewhere that they were considering adding Bossa Nova in the 60's, but determined that it was too much of a passing fad, and that the other dances could be preserved and enjoyed longer because of the impact they were having on the social scene. The same is true for Mambo over here, and leaving Mambo where it is preserves something from the past.
Now, it's true that the Mambo danced now is not our Grandma's Mambo, but that's true about the Waltz, and Tango, too. I don't mind that Mambo has been slowly influenced by passing trends (like Disco moves in the 70's, or FlashDance moves in the 80's, or Salsa moves in the 90's/00's), but the core definition of what Mambo was is still preserved - an On 2 basic, and sharp/steccatto hip and leg actions.
As for the differences Mambo and Salsa have to me, I agree that when a Salsa song comes on, you can tell a sharp action would not be appropriate. You have to hang back and blend the figures. I also personally like breaking on 3 when I dance Salsa (like a fast American Rumba count), that way, I don't have to count - I can just ride the bass-line.
Mambo music, to me, is the old greats, like Tito Puente, Celia Cruz, or the big band renditions of Latin music played by Perez Prado, Xavier Cugat, and other greats.
Ballroom is kind of like a Conservative dance movement, preserving things from the past, but slowly letting in pieces of the new by outside influences or successful innovators from within.
In that case, it appears that what the masses do socially in the ballroom world and what the championship competitors do in front of the judges should meet somewhere in the middle, in order to consider changing any of the dances.
[/img]