Updated post: A reliable source is letting us know we should go to El Quijote very soon. In the interest of protecting the source's source, I've been asked not to say more at this time, and to delete the details previously shared in this post.
All I've agreed to say is this: El Quijote has been in the Chelsea Hotel since 1930. It hasn't changed much since, and if you'd like to experience it as it's always been, go have a good, affordable meal while you still can. Changes are coming.
Update: My information has now been confirmed via Eater.