From all the rumors and leaks thus far, many of the features and themes from Assassin's Creed Ragnarok match many of the aspects of Assassin's Creed 4: Black Flag from 2013. Both circumstantially and thematically, these rumors point to an Assassin's Creed game that foregoes the standard nature of the Assassins as fans know them. Much like how Black Flag was a rogue departure for the Assassin's Creed series as a whole, Ragnarok appears to be gearing up for a similar shake up to the franchise's formula.
Gameplay in Ragnarok would almost certainly involve a greater focus on ship traversal and possibly combat, a defining aspect of Viking movement and conquering. The use of their revolutionary Viking longships helped facilitate the great expansion of Scandinavian societies, as it allowed Vikings' ships to be very nimble and could invade territories with haste and ease. Viking ships were integral to their culture as well, held in high regard and religious importance to Norse mythology. Expect some scrappy ship combat tied into the raiding and pillaging of Germanic communities.
Ship combat will also likely differ greatly from what was in Odyssey, for a few reasons. Culturally, Vikings believed that ranged weaponry of any kind was considered less honorable, and generally preferred grounded melee combat with a sense of pride. Along with that Viking longships weren't nearly as big as the warships from the Peloponnesian War in Odyssey, meaning don't expect large scale ship combat. Instead it's more likely that ship combat will be a slightly rarer occurrence but much more tense. Assuming players enjoyed boarding enemy ships, expect more of that in Ragnarok. Viking ships were incredibly flexible and nimble for their time, so it's likely any ship combat in Ragnarok will have a lot of freedom of movement, making any naval fights faster and more hectic.
Whether this is a coincidence or not, Assassin's Creed Ragnarok and Assassin's Creed 4: Black Flag both have a very similar release timing. In the transition between the seventh and eighth generation, Black Flag released simultaneously on both PS4/Xbox One as well as PS3/Xbox 360. With Ragnarok reportedly coming out at the end of 2020, there's a high likelihood it will release cross-generation between this fall's newest consoles and the current generation. Whether this happened by chance or not, it's an interesting correlation considering what the two games symbolized.
Assassin's Creed 4: Black Flag was a great departure from the seriousness and impending doom feeling that the overarching Assassin's Creed narrative had been building up to since 2007. After the climactic events of Assassin's Creed 3, it was almost like a brief year-long reprieve for the franchise despite Black Flag being a mainline game and not an Assassin's Creed spinoff. Of course the Assassins vs. Templars narrative returned in full force with Assassin's Creed Unity, but Black Flag was significant in that it's gameplay and story invoked a pervasive feeling of freedom unbridled by the tenets of the Creed. Assassin's Creed Ragnarok, taking place in a Viking period that's likely several years before the formation of the Templars in the first place, is likely going to have a similarly changed atmosphere.
Building off that, Ragnarok could even be the game that strays the furthest from typical Assassin's Creed fanfare. The Viking age was a brutal time during which Scandinavian explorers left their homes of what's now known as Norway, Sweden, and Denmark to expand and raid other existing Germanic communities. Vikings are characterized as brutal explorers pillaging those they believed were weak in order to strengthen their feudal societies. Obviously pirates performed similarly disgraceful or abhorrent acts like in Black Flag, but never to the extent of the brutality often depicted in Viking media.
That's part of the reason why Ragnarok has the potential to be very different. Jora, or whomever the protagonist of Ragnarok will be, will likely find themselves in morally ambiguous/awful situations during the story that need to be done. Even though the word Viking was a Scandinavian term for "pirate," they're not akin to Black Flag's pirates. Edward Kenway and his band of pirates strived for freedom under the guise of a noble cause, and while they weren't exactly heroes, didn't canonically brutalize just for the sake of expanding and conquering. How the actions of the Vikings may tie into Assassin sensibilities (other than perhaps taking the "nothing is true, everything is permitted" tenet literally and liberally) becomes much more implausible.
According to Assassin's Creed lore, fans know the Templars have existed far longer than their real-world history's formation in 1119 CE. How Templars or Tainted Ones may appear in Ragnarok remains to be seen, but they had have to be plotting something far more brutal than what Vikings were capable of. Fans should more likely expect a version of the Assassins, or in this case "Hidden Ones," that still favors brute force and public violence to achieve their goals. Similar to Kenway at the end of Black Flag, we could see a sort of reformation for Ragnarok's protagonist to perhaps change the ways of the Vikings on the way to the new second CE millennium.
Whether or not the protagonist partakes in such aggressive conquering behavior remains to be seen, but Ragnarok's place in the Assassin's Creed universe is going to be far removed from what is expected of the titular heroes of the series. Overall, the transition to Viking-era history for Assassin's Creed should be savagely interesting, as the interweaving of the franchise's narrative into the brutal Norse world within 793–1066 CE is going to be ambiguous and fascinating.
Assassin's Creed Ragnarok is reportedly in development for holiday 2020.