Isn't the purpose of a definition to clarify communication? How would changing the 1954 definion clarify communication?
If we wish to talk or write about something that fits the 1954 definition, then we have precisely the word we need. If we want to talk or write about something that doesn't fit that definition, then we can use other terms.   
Suppose we are trying to talk about violins. Suppose further that I have updated my definition of "violin" to include violas, cellos, and basses.
Wouldn't you rather I say "violin" when I mean "violin" and say "bowed instrument" when I mean "bowed instrument"?
Kent