No tool led to their appearance or disappearance just prevailing tastes and fashions. However, pronouns such as I, it, he, she , and we have remained unchanged for centuries and it is doubtful that e-mail will do much to drive them out of the language. As a student and teacher of language and linguistics, I find the attention this topic has received to be a little silly. Language, like its speakers, evolves. But other than certain cosmetic features, these changes are very slow.
People change clothes everyday, but internally they remain largely unchanged.
Instead of bemoaning the loss of the semicolon, celebrate the increased use of the tool of writing. The language will be fine. It s a survivor.