It's a long running fad, I expect it to die down eventually, it's already becoming over exposed.
It became cool back when Anne Rice and others were popularizing a fairly "new" take on the vampire idea, along with movies like "The Lost Boys" and PnP RPGs like "Nightlife" (which was before Vampire The Masquerade) it was a fairly "cult" thing.
Over a period of time it got more popular as people started to emulate it, eventually it exploded into it's own "Paranormal Romance" genere and despite becoming as mainstream as apple pie, managed to keep a somewhat subversive tone that convinces a lot of the pudgy housewives and unpopular teen girls that for some reason they are reading fairly "unique" or "underground" takes on the concepts, when in reality they are reading the same stuff as pretty much everyone else.
Heck, nowadays you've even got Harlequin involved.
I anticipate that we're pretty much seeing the bubble right now, where that fanbase is fairly happy that ie became relatively mainstream and is even getting relatively high quality TV treatments like "True Blood" (in comparison to the comparitively low quality "Forever Knight").
The bubble will probably burst in a few years when everyone realizes how coke and pepsi the whole thing has gotten, and how long it has been that way. Then people will move away from it to find something to fill a similar niche. Sure it will always be there, but no longer as prolific. Eventually people will probably look back on the genere as the whole "Paranormal Romance/Vampire vibe that they had going between like 1995 and 2012" (or whatever the general dates tun out to be).
Inevitably people will try and capture those same elements for later works, but it won't be everywhere.
Badly written (I'm tired), but basically your not the only one thinking the whole "It's soooo goth to be dead" vampire schtick is becoming overdone, as it really is everywhere. But we've been here before with other things. It takes time, but it will pass, it always does.
Every single long running fad goes through a period where people generally fall into the catagory of those gleefully surfing the wave before the inevitable crash, and those contemplating drilling their eyeballs out as they feel the crash can't happen quick enough.
I personally thought the ideas were cool to begin with, but am now sick of the genere because it's been beaten to death. Twilight simply represents the final mainstream evolution that the genere had been working towards. That is likely the biggest face people will remember the movement's height by, and ultimatly the face it will crash wearing.