Those who played STORY OF SEASONS: Friends of Mineral Town might remember that the game featured a "Best Friends Ceremony" that basically allowed for same-sex marriage. It looks like that feature is being retained for STORY OF SEASONS: Pioneers of Olive Town.
According to the Japanese site for the game, you'll once again be able to marry whoever you want. A fan-translation of a specific page of the Japanese website reads as follows.
"There are 5 bachelors and bachelorettes to romance, making them 10 romance options in total. It is possible to become partners with the same-sex through a 'best friend ceremony'."
This information is yet to be confirmed on the official English site, but that content should be coming sometime soon.