I don't see how it would matter, not only from a moral standpoint but a gameplay one.
I mean, the only way we'd know he was gay is if they outright told us (like Rowling did with Dumbledore, in which case it would have no impact on the game at all, the way Dumbledore's outing had no impact on the books at all) or if they put in a romantic sub-plot. With a romantic sub-plot (Link x Groose, anyone?) there are two ways it could go, as far as I see it. It could either be a subtle thing that never really becomes important at any point and so has very little significance or it could be a lot more obvious and feel like Nintendo were trying to make some kind of statement which I feel could be distracting and make the game lose focus.
So to answer the question, I don't think having a gay Link would ruin the franchise and it wouldn't stop me from buying the game at all. However, depending on how Link's sexuality is displayed and used in the game, it could be something inconsequential and therefore not worth it (eg. Dumbledore) or it could be something which feel out of place due to too much focus on sexuality.
Explain Tingle then
Tingle isn't a homosexual. He does not limit himself to one specific gender. Men, women, the pigs of Outset, the Rito and Gorons, the Zoras and even the Deku Scrubs cannot avoid his uninhibited sexual passion.
If it has a hole, Tingle will love it