If there's not a Doom/Ghost Train, and Godbert doesn't show up to defeat it by suplexing it, I'm going to be VERY disappointed. We've had those train tracks in Thanalan since the beginning of ARR, btw, and to my knowledge, they're still not being used for anything.
Investigating rumours of a phantom train on those track (or similar other worldly activities) with everybody's favourite detective sounds like a cool idea! :)