Lol I feel like I am in a similar boat as you are, except my guild
had BWL on farm. Now between MIAs & /gquits & /game-quits we struggle just to put together a competent 40-man raid. We couldn't even get past Razorgore last night, & AQ40 progression has become all but a dream. Really the only thing keeping me going is 1.) I'm an active officer of this guild & know it would be harmful to my friends if I just up & left, 2.) I have a lot of DKP & would like to get a power-item before the expansion comes out, & 3.) I haven't found any other good game to play instead. I intend to keep at it until the expansion comes out, at which point the game will change entirely & I can find a new "walk of life".
If I were in your shoes, I think I would push my guild to get Nefarian down at least once before the expansion comes out, b/c it's a significant accomplishment to both a guild & a gamer that will effectively become impossible to replicate after the expansion comes out. I have been a part of every first-down our guild has ever had (except Broodlord!

), & it's something I will always treasure. If you think as I do, scheme to see what you can do to maximize your raid's effectiveness--post boss strategies on your guild's website & pressure ppl to read them, provide consumeables for new encounters (things like Nightfin Soup & Lesser Mana Oil aren't terribly hard to get), ask your class leaders to start requiring ppl to get enchants, etc. If that
doesn't appeal to you, though, I concur w/ the others: find something to do that does. /Gquit & find a new raid, go grind to exhalted w/ all three BG-factions, pick flowers, gank lowbees, whatever. The (virtual) world is your oyster.