An aside, to supply some facts, as opposed to speculation:
Since the Wizard's Attic implosion and the truncation of efforts on the Dragon Lords of Melnibone d20 line, Chaosium have also published two Eternal Champion monographs: Gods of Chaos (in 2004) and, more recently with Darcsyde and Lawrence Whitaker's cooperation, the new Hawkmoon (a specifically written "sub-set" of the larger work Darcsyde still hope to publish at some date). They also have at least two other EC monographs near completion: Charles Green's Gods of Law sequel to Gods of Chaos and Richard Watt's A Guide to Old Hrolmar. Plus there are a couple of other's being worked on I believe. Meanwhile some 11 existing titles are available in print form from Chaosium that support Stormbringer 5 (inclduing the Core rulebook), and 17 (including several previous editions of the core rules and the old 1980's version of Hawkmoon) are available as watermarked PDF's from Drive-Thru RPG.
Hardly "a dead product line". Whether it's "good enough" is debatable - but not, I'd suggest, in a thread about Mongoose's new RuneQuest and Lankhmar books.
Now, back at the topic, how do folk imagine Nehwon should be dealt with in terms of sourcebook(s)? Leiber was, in the Fafhrd & Mouser stories at least, definetly a writer of the pulp style, where invention and wit were far more important than meticulous world building. Adding simple factual detail to Nehwon to enable a game is frankly trivially easy - doing so in a fashion which captures Leiber's sense of irony, dark humour and poetic sense of invention is trickier, but surely essential to enable games that actually "feel" right?
So would people really want to see a Lankhmar sourcebook and a Quarmall sourcebook and an Ool-Hrusp sourcebook etc etc etc? Or is there a different paradigm that might suit Nehwon better?
Cheers,
NDM