Expansion Packs
You can pretty much guarantee there will expansion packs. What’s in them, and when the first one will arrive, is completely up in the air. If ArenaNet even know what they’re putting in their first expansion and when it will get released, they aren’t telling.
They will likely do this, as they did with GW1. There’s also a huge thread in general discussion about adding some previous areas in GW1 into GW2, namely Cantha.