“They” has, in fact, been popular for gender neutral singular use since before the Latin-inspired prescriptivist movement and its attempts to install as “correct” various things that were previously either not dominant or in some cases entirely foreign to English; that movement's influence had actually been fading on that usage and in general for decades even before concerns about sexism in language became significant; singular “they” is no more incorrect than the now-so-universal-most-have-forgotten-the-actual-singular use of the second-person plural when the semantics are in fact singular.
