To toot my own horn, I called the Ragnar/Christianity angle a couple weeks ago. I saw that one coming with how enamored he was with Athlestan from when they raided England and captured him.
I also agree that we are about to see the end of Ragnar, which is really unfortunate. I felt like there was more to develop with his character and I just really like him. Ragnar made some comments alluding to his departure. When speaking with everyone about negotiating with Paris, he talked about how he became Earl and then King not on his own ambitions, but because of the actions of others. Thus setting the stage that one of them would be become King because of his actions making it necessary. Personally, I predict that Ragnar is going to ask Bjorn to kill him and end his suffering, thus making Bjorn king and keeping it from Rollo.
-Mike