Indoctrination Theory 2.0? 
Although, admittedly, that theory was more of a byproduct of the denial stage...
Of course. The Warden and Leliana made a plan. They need to disappear and be left alone, so they will want the world to think whatever the devs will decide, but they really are going to Tuchanka/Bahamas/Skyrim/some mysterious unexplored continent in Thedas/add your own custom setting. Leliana foreshadows what it's going to happen at the end of DA2. She just doesn't tell Casandra she is going to disappear too, just like Hawke and the HoF. Unfortunately the whole Coryfish thing and the breach in the sky complicated things a bit.
The quest to cure the Calling is a McGuffin. The HoF cured himself/herself of the Calling after Awakening because of his/her own awesomeness. Why do you think they don't show the content of the Hof letter to Sister Nightingale?
May I have my tinfoil hat back now, please?