We have 2 possibilities, right? Male/Female Link and Link/Female Other char (for the sake of argument, let's say impa). The second possibility can result in 2 types of games also. One where Link existing causes the other to not exist (and vice versa), and one where they both exist and their actions complement one another.
So in a Male/Female link game, you can have nothing but gender-neutral encounters. Interactions are for a goal/motivation other than a romance/crush. If nintendo's super progressive, then they can make romance stuff in there, but then your choice also affects other NPC's gender preferences somehow - which may be off putting. The other option is that *IF* you encounter something that would be romantic, you write it two ways. Any romance would exist for male doesn't exist for female, and vice-versa. Maybe dudes hit on you if you pick female link, but they don't hit on you if you pick male link, etc. You now have 'bonus' cutscenes depending on which gender you pick. This offers some replay.
The other possibility, the one I like more, is that there are 2 different playable characters. I like this MORE because it likely means you get 2 games in one (or at the very least, 2 very different sets of cutscenes, ideally). If they play differently, that means you get 2 gameplay styles in one world, which is fantastic. Offers a ton of replay value. It also likely means that each character has entirely different actions and interactions with other key NPCs. If it's, say, impa, she has a duty to protect the kingdom of hyrule, so she does what she can to protect it. A different motivation from what link usually has, which is that he's chosen by the goddesses to save the world from evil. It's his sole purpose in life, versus impa's inherited duty/loyalty to the throne. In an open world, this could drastically change dungeon order, key cutscenes, and even the items/powerups you find.
While male/female link is neat and progressive, I really doubt it'll change the game that much depending on which one you pick. I think it'd be a cool 'bonus' to be able to choose female link, but it's nothing groundbreaking or gamechanging for the series. Being able to pick one of two major protagonists with different paths/stories would be. It'd offer up a ton of replay value for a franchise that severely lacks it.