I'll never understand fans who think the original timeline was overwritten. I think some people forget that this is all just made up. The rules are whatever the storytellers want them to be. And no storyteller is going to want to say that the Star Trek
we've been fans of for 45 years has somehow "ceased to exist." The whole reason Abrams & co. created the alternate timeline in the first place was because
they wanted to leave the old timeline intact and unaltered. (Also because they're using plausible, informed physics in which different timelines always coexist rather than overwriting each other.)
Not to mention that, since it is
all just a bunch of stories anyway, those stories aren't going anywhere. As long as you can still watch the episodes and movies and read the old books, nothing's been "erased."