OK. So let me get this straight. You only know that this will be a 224 page hardcover full colour book focused on Drow, from WotC, coming out around the announced time, and this eventuality bothers you because: a) it has, to your way of thinking, too narrow a focus; and b) it *might* (and, let it be said, equally might not) consist largely - or entirely - of reprinted and/or reworded and/or restatted material.
As that stands, 'b' applies as well to hm. . . the MM for starters. And many more. And 'a' could apply to the Draconomicon, for example.
Soooo. . . is there anything I'm missing here?
Yeah, you are. Most notably, The word "and." A narrow focus on something brand new or fairly unexplored could be pretty amazing. Check out what Lords of Madness did with one species that didn't really have much about them before they were covered there, and one that was brand new for an example of that. Or what the Tome of Battle did -- a narrow focus on a new mechanic that made it cool. Even something that's just a little rare, such as the Fey or Giants, could be awesome, because everyone knows they're around, but few people see a reason to use them.
And you're missing the fact that dragons are quite a varied monster. Different types, subtypes, alignments, energies, appearances, goals, motivations, CR's....compared to drow, dragons are exceedingly diverse. Drow have one alignment, one CR, one appearance, one subtype, one type. Drow are drow. Dragons are red dragons and copper dragons and wyverns and faerie dragons and abyssal drakes and landwyrms. It would be a hard case to argue that dragons are a narrow focus.
You're also missing the fact that the MM is one of the core rulebooks of a new edition, and is thus required to update the rules. I'm not sure what drow-specific rules are so important in older editions that they need an update now that they haven't had one for six and a half years. I still had a problem with the Spell Compendium because it is simply repackaged and slightly updated material, rather than something new, making it a fairly broad focus with existing or recent material that wasn't key to the game anyway.
That said, something like the Fiendish Codexies get something of a pass because in the case of FCI, there was a wealth of new information on a very broad range of creatures. FCII promises to be slightly less in that regard, it appears, but it's still good info on a broad range of threats, from CR1-20, from fire-subtype to cold-subtype, with spell-like abilities and an alien culture that didn't have several novel's worth of information to accompany it.
But you're broadly right. The drow are a narrow focus that have been well-covered already. A new coverage or a broader focus would definately make me less hostile toward the title.
Um. Right. So, who exactly was expecting you to "stand up and applaud WotC for giving us the same stuff with new artwork" in the first place. . . ? And really, how can a book you know practically nothing about demonstrate any value to you? That's hilarious.
What I do know about it can demonstrate value to me. For instance, I know virtually nothing about Dungeonscape, the upcoming title that focuses on dungeon environments. Yet it demonstrates value to me by being about something that is key to many people's games (not just my own!) that has recieved little new work since 3e came out. Now, that could go wrong...it could just update the Book of Challenges, for instance.
But it has show that it has value for me by being about a narrow focus that has not been the subject of much recent conversation. It's new and exciting!
Or, take the Magic Item Compendium, which I'm actually kind of excited about. There's a new magic item format that can add a lot of interesting details to that which has already been mentioned, and there's possibility for new treasure charts and the like so that rolling them up won't be hard. Magic items were once prolific, but aren't really, anymore. They're also used in probably 100% of the D&D games in existence in some form or another.
But drow have no value to me.
And, for that matter, it does seem that you "place value on the simple fact that there are drow in something". . . negative value, yes. But still.
No, it's a null value. A negative value would suggest I want to stop people who want it from buying it, to actively hinder it's success, and I really don't. Take it and have fun. Just like with the Spell Compendium.
I do, however, place a negative value on a lack of new creative energy. Which the Spell Compendium definately displays, and a book on drow certainly threatens to display.
. At least it's not another dragon-based book. I'll definitely page through it in great eagerness. That might be all I do, as I already own piles of drow information. 
