I imagine the next Eldar Codex is a fair way away, and there's an even-to-good chance that that release will be a single model and that's it.
To put it another way: Outside of new/obviously unfinished armies that got 'half' Codices (Sisters 8th, Lumineth 1st, and more recently NotSquats 9th), how many armies have had a big release followed up by a new book with an equally big release, and also doesn't rhyme with
"Race Kareems"?