I still think Nero makes it out of WoD more or less alive and will be the one that mentors DRK in 3.0. I think he'll end up in Gridania since there's no tank guild there yet.

As to the Main Story surprise, I think that most people have felt a little conflicted fighting Shiva as her goals pretty much align with ours. The Keeper of the Lake will probably show us that the Dravanians are on our side - which is fairly obvious considering they fought against the Garlean invasion as well - and that the real issue is the religious nutters that control Ishgard. The Battle for Ishgard will be about changing that regime to one that is more friendly to outsiders (so we can get in) and which can reach a truce with the Dravanians (so we can get out into the skies beyond it without having to fight Dragons all the time). I assume that we'll have Frosty (Iceheart) on our side in that battle (though not in Shiva form). I suspect that we will find that the leadership in Ishgard is really in control of the Dravanian Horde, and uses them to justify their autocratic rule. So I suspect we will battle the Ishgard leadership, both in human and in dragon form.