We will certainly see them go to Iceland. The rest is in the lap of the gods.
Earlier in the year, actor Adam Copeland (a.k.a. former WWE star Edge) revealed he would have a recurring role in Season 5 of Vikings, in which he would play a Viking charged with setting up a colony in Iceland. Now that we know from Michael Hirst's Reddit AMA that Iceland is for sure happening, it goes without saying that we will at the very least see a significant change of scenery in Season 5. It's more than fair to assume Iceland will not be the only location being traveled to in this season!
While I can't speculate as to how many places will be visited in Season 5 of Vikings, I can go back to the original question posed on Reddit, which asked if Iceland, Greenland or the USA will be featured, and definitely rule out the good old U.S.A. Common sense says that if Season 5 features a story of the warriors setting up colonies in Iceland, there are incredibly low odds we're going to see a journey to America nearly 5,000 miles away. I'm not entirely confident on Greenland, but it's also over 2,000 miles away, so I think we can more than likely rule out any Vikings getting there in the near future.
Fans of the series have debated where the true setting of Vikings lies, it's clear that Iceland is not one of those locations. In a historical context, Iceland is believed to be founded by the Norsemen somewhere around the 9th century. While it is widely believed that the Vikings were the first to roam Iceland, there's actually evidence that Gaelic monks might have roamed the land prior to the Viking arrival. No word on whether or not the two ever met, though.
_*Spoilers below for anyone who hasn't yet seen the Season 4 finale. *_One of the big reasons to assume more locations comes after the shocking finale that happened Wednesday, in which we saw Ivar's post-victory raves about pushing onward and conquering more lands. which soon led to him killing his brother Sigurd. Obviously, this action won't sit well with the rest of the sons of Ragnar who have been at odds throughout most of the season anyway. Sigurd wasn't the only casualty, either, as we witnessed the death of Helga, who has been with the series since its beginning (and is also a daughter to creator Michael Hirst), as well as former King Ecbert.
While we don't know for certain all the places Season 5 of Vikings will take us, I think it's safe to assume it'll be a wild ride regardless! We'll hopefully get to see Season 5 taking over in 2017, and while we wait, jump on over to our midseason premiere schedule to find another show to dive into!