Season 3? At the pace they're going at now, I wouldn't expect to see Alfred the Great until season 4 or 5.
Season 1 had 9, count them, 9 episodes, and I see no reason to believe that season 2 will not follow suit, which means we're about halfway into season 2.
Ragnar Lodbrok is still among the living at this point, and it was his death, and the manner thereof which was the proximate cause (read: excuse) for "The Great Pagan Invasion" which propelled a young King Alfred of Wessex to the prominence he had in stopping, but not being able to reverse.
To do justice to that, in the manner in which the producers of the series have elected to pursue, would require a very quick time jump, which I don't think we'll see...
the infowarrior
You may be right maybe season 4 if they do get it I want see that
Season 2 and 3 will be 10 episodes.