First thing i would like to say is this: This is not confirmed yet, only hinted at recently in this WoW thread World of Warcraft - English (NA) Forums -> Quel'Serrar
Now, here's two quotes for those who didn't care to go to it (from a blue)
1. The Quel'Serrar will continue to exist... in one form or another. The compendium of dragonslaying may not be so fortunate.
2. The tier 2 helms aren't the only models we wanted to reuse, that's all I'm saying.
For those who don't know the book: http://www.wowhead.com/?item=18401#comments The final part in the quest requires you to place the unfired blade in front of Onyxia during a breath, which ultimately leads to: http://www.wowhead.com/?item=18348
Now that that is out of the way, here's my conclusion. There are plenty of collectors in WoW that are willing to buy this book now at a reasonable price (500-1500g or so atm). The book is pretty rare, and if you planned to farm it go ahead. Mostly, this post is a warning for those collectors out there who ignored grabbing this sword for now (Quel'Serrar). It was hinted, as you can see in the post, that a new Quel'Serrar may exist when the new Ony is released, but, for those collectors, it will never match the epicness of what was known as Quel'Serrar.
[ame="http://www.youtube.com/watch?v=s7x2U-ro8p8"]YouTube - Blackulaa - Shield Hearth[/ame]
On a side note, with the removal of this item, the price will soon go much higher. Currently, not many people at all know about this because the thread/question was so recent, as was the blue response. If you want to head over to Dire Maul and farm this, have a blast. The drop rate is low and the chances of getting one are (obviously) low. Your other option is to head to the AH and hope there is a cheap one up, grab it, and save it for later when this becomes more public. I don't know if the book itself will cease to exist when the next patch comes out, but my feeling is the quest will be unable to be completed so I would assume you would want to wait til a week or so before the patch and AH it fairly high.