So how quickly does "pre-existing reality" shift before it starts to alarm you?
I don't think that question makes any sense.
All that matters here is that this change is simply an update to the wording of the statutes. Gays can already get married. This isn't enabling that. This has no practical effect, it is just fixing what is otherwise nonsensical wording. The statute said "husband" and "wife" even though *it's already the law* that two guys or two girls can get married.
You don't need to pretend that this is the end of the world in order to demonstrate disapproval of gay marriage.