We have seen a few portals/rifts in various different places in Fortnite. The first three portals were found at the Motel in Lonely Lodge, the ‘Noms’ restaurant in Retail Row and the ‘Durrr Burger’ restaurant in Greasy Grove. At all of these locations, the rifts have consumed the signs and there has been one more rift that has been located after at a mountain in between Snobby Shores and Greasy Grove. This rift has been different from the others as we have seen an anchor appear instead of seeing anything disappear.
It seems as though there will be two more rifts that still need to occur, as there have been oddities that were leaked by @FNLeak which have either disappeared or appeared.
The items left to appear are the Desert Skeleton and the Wild West Stagecoach, so from this we can assume that there will be two more rifts that will appear to place these items somewhere on the map.
The anchor has been found on the mountain in the middle of Greasy Grove and Snobby Shore. It is unclear where these new rifts will be located and which will be the next item to be coming to Fortnite.
It seems as though the historical theme for Season 5 is pretty much confirmed with the new objects that should be coming.