I don't think that Nintendo would ever create a whole separate series of Zelda from the actual series. Also, I definitely believe that there will never be a LinkXZelda relationship shown in the game. I think that is more for the people out there that have a creative mind and write their own stories of what Link and Zelda could have as a couple. I also believe that it wouldn't look good for Zelda to be in a relationship. She is to be protecting and ruling over Hyrule. Being in a relationship with Link could distract both of them from their duties and what they have to do to keep Hyrule from crumbling to pieces. Being in a relationship can definitely be a large distraction and, again, that would not be good for the future fate of Hyrule. I would not expect nor would I hope to see Link and Zelda be shown as having a relationship in the Zelda series and games. There may be portions of the games that you have played that would make you feel as if a relationship were possible between Link and Zelda, but I highly doubt that Nintendo would ever incorporate that in the game itself.