Nintendo wouldn't wouldn't do that as Link was made to have a connection with the player, hence the lack of "personality" and why he's called Link.
As for video games in general if the lead character was gay this wouldn't bother me, whether it was a major or minor thing. If there was some long make out scene between 2 dudes then i'd feel a little uncomfortable as I don't swing that way but that detail wouldn't put me of a good game.
I'd definitely not play that one game, it would definitely not ruin the previous games, as for future games if they would be completely uninfluenced by that game then it's fine (e.g. if that one game was developed completely by another studio).
Not that they ever would, but I guess it'd depend on how they went with it. If they turned the game into a total male harem, I'd have an issue with it. If the core idea of the games stayed the same (one childhood love interest, the prince(ss), the bad guy(girl?), but otherwise varied cast of both male and female characters), then I'd happily play it.
Because a character in a game being homosexual is a legitimate reason not to play it?
Link is a mindless submissive anyway so it isn't going to make a difference to the gameplay or narrative if he is or isn't homosexual because unless someone tells him to go and get it on with another guy to save Hyrule he isn't going to act upon his orientated desires.