I suggested the Lords of Waterdeep several times as the paid expansion for 2015. If that doesn't happen for whatever reason, another large expansion could be the Forgotten Realms' Maztica. This Central American Aztec / Mayan area would be unusual among MMOs and would not require new rules or even much in the way of new art resources. The Latin American players would probably love to see something like this added to DDO.
http://forgottenrealms.wikia.com/wik...a_Campaign_Set
What do you think? Maztica would also offer the opportunity to introduce some other suggestions that have been offered on this sub-forum, such as the panther / jaguar druid, the Shaman class, and new monsters like a Giant Demon Bat!