If atheism is the "default" then should atheists be re-named "non-theists"?

actually, yes, it's a misnomer. but as long as there are more, or at least a reasonable amount of theists the name will be atheist. After that, there won't be a name, because everyone is an atheist (Just the fact that we don't have a name for people who don't have three ears, nobody has three ears)