I don't know how many weapons from BC would have the same sort of nostalgia that old world weapons have.

Also, the underlying motivation might not really be there. Azeroth content needs an update, and updated weapons make sense to go along with that. I don't know that they would ever retune BC content to the extent they are doing Azeroth. While BC certainly had some stylistic complaints, the experience of it is much, much tighter than the original game.

The old world has several zones that just plain did not work or were never really finished. Which is fine, really, since Blizzard has shown a remarkable ability to learn from their early design and improve greatly on them. In the somewhat tedious Gelkis/Magram quests in Desolace lay the seeds for the Aldors and Scryer, and subsequently the Frenzyheart and Oracles. Painful zone layouts, like Azshara, led to much slicker zones with multiple flight points found in BC and Wrath.

This brings up an interesting question: what are the things they absolutely need to fix while revisiting Azeroth? We already know that Desolace and Azshara, two relatively unpleasant zones, will get significantly redone. Orgrimmar is apparently being redesigned.

I hoping (and expecting) that Quel'Thalas and the Azuremyst Isles will get incorporated into the rest of Azeroth rather than being on a separate server. One zone I really hope they revamp is Winterspring - the most beautiful zone in the original game, but quests are limited to a goblin town that doesn't really have any reason to be there, and the questlines are mostly unmemorable as a result. And Feralas definitely needs an Alliance camp on the mainland...

I won't be surprised if that island is now underwater in Cataclysm anyway. After all, flooding is supposedly going to play a big part in changing the landscape.