This goes in the category of absolutely (likely, anyway) excellent reference works that nobody can afford, but everybody should have. Brill is publishing their Encyclopedia of Ancient Greek Language and Linguistics very soon. It’ll be available in July at the very low price of $1100; though Amazon is already ahead of the gram with a $55 discounted pre-order price. So, I guess if you have any swing with an academic library’s purchasing plans, maybe make a recommendation and hope that your library still has the semblance of a budget.
There’s a PDF Preview available (link), too, though it looks like some of the articles have been reduced in length for the preview.
Also, at this price, Brill had really better give this set an absolutely immaculate binding.
Brill’s Product Description:
The Encyclopedia of Ancient Greek Language and Linguistics (EAGLL) brings together the latest research from across a range of disciplines contributing to our knowledge of Ancient Greek. The EAGLL offers a systematic and comprehensive treatment of all aspects of the history and study of Ancient Greek, comprising detailed descriptions of the language from Proto-Greek to koine. It addresses linguistic aspects from several perspectives, including history, structure, individual singularities, biographical references, schools of thought, technical meta-language, sociolinguistic issues, dialects, didactics, translation practices, generic issues, Greek in relation to other languages, etc., and on all levels of analysis including phonetics, phonology, morphology, syntax, lexicon, semantics, stylistics, etc. It also includes all the necessary background information regarding the roots of Greek in Indo-European. As and when, excursions may be made to later stages of the language, e.g. Byzantine or even later. The focus, however, will predominantly be Ancient Greek. With well over 500 entries on all aspects of Ancient Greek, this new encyclopedia is the authoritative reference work for students and researchers of Ancient Greek, general linguistics, Indo-European languages, and Biblical literature.