The Hobbits are going to Isengard! I spoke to LOTRO's Executive Producer Kate Paiz at E3, and he told me "We're definitely planning to get players to Isengard next year".
Isengard is the tower of Sauramon the White, Gandalf's former friend who works for Sauron (the bad guy), and the setting for one of the most epic wizard battles in the entire LotR series. A central figure in several key moments in the storyline, it hasn't been decided yet how involved the players will be in with Sauramon's plight - but there is precedence for players taking control of central lore figures to act out these types of big moments.
Paiz also told us that they're going to wait and see how players react to content packs (as opposed to expansions) before deciding if Isengard will be part of a content pack purchased through the in-game cash shop, or a full expansion.