'Vikings' season 4 spoilers, air date, plot rumors: Story of Ivar the Boneless to be explored; Ragnar to be killed by one of his sons?

After the six-year time jump unveiled Ragnar Lothbrok's (Travis Fimmel) sons all-grown-up, fans became more excited to see the return of "Vikings" season 4. Although the reason for Ragnar's impending death remains to be seen, there are several fan theories on how he will die in the story.
Since Ivar (Alex Hogh Andersen), Ubbe (Jordan Patrick Smith), Hvitserk (Marco Ilso) and Sigurd (David Lindstrom) are now full-grown men, they will each have different reactions to the return of their prodigal father. Rumor has it that the King of Kattegat will be killed by one of his sons out of rage. Other reports claim that instead of being murdered in cold blood, Ragnar will succumb to an extreme kind of disease at the end of the war in Paris. It is also believed that he will be captured by his enemy, the King of Northumbria, before being thrown into a snake pit. If one thing is for certain, Ragnar will meet his fate in season 4 and one of his four sons will inherit the throne.
Based on the history books, Ivar is dubbed as one of the most famous vikings who ever lived. As the series moves forward, Ivar's story and his Great Heathen Army will possibly be explored. Bjorn (Alexander Ludwig) is also set to have a bigger role since he will be setting sail for the mystical Mediterranean but before his journey even begins, he must approach his uncle Rollo (Clive Standen) to ask help for a safe passage.
Actor Jonathan Rhys will be joining the cast this season for a yet-to-be-announced role. It was previously hinted that his character will have a significant role in Ragnar's death, but it remains to be revealed if he will be responsible for the King's demise. Prior to the show's return this year, History already greenlit a fifth season for "Vikings" set to air sometime next year.
The second half of "Vikings" season 4 is expected to premiere sometime this Fall on History channel.