I think Dragon Isles would be a cool addition if it included a revamped max-level Quel'thalas too.
Dragon Isles appears on the WOTLK beta map, north of Strat and West of Quel'thalas.
I think it would be cool if we got Dragon Isles, but instead of the DI being the whole expansion area, it takes advantage of the geography to reboot Quel'thalas and 'New Lordaeron' as well. Silvermoon could be updated and be used as the Horde capital hub and Stratholme could be rebuilt to be the Alliance hub.