Link from The Legend of Zelda has always been a Hylian, and it turns out that there is a lore-based reason for that. It's a piece of information that explains why Link always looks so similar, and almost always ends up saving Zelda. Even as the series sees different versions of Hyrule and different lands, Link's appearance remains a constant.
Link's design in the series is ingrained in gaming history - he's an elf-like man with blond hair and pointed ears. He wields a sword and shield as his chosen weapons, and wears a green tunic and hat as his iconic outfit.There have been a few adjustments to the design, such as Ocarina of Time and Majora's Mask's young Link, and Wind Waker's toon style that Miyamoto initially disliked, but the biggest departure from this design was in Breath of the Wild, where Link's main outfit is a blue tunic with white accents, although his classic outfit is also available.
Link Possesses The Legend Of Zelda's Spirit Of The Hero
Link having roughly the same design every time seems like a way to keep the protagonist's design consistent over multiple games. However, Link's quasi-reincarnation is actually the result of a curse placed on himself, Princess Zelda, and - by extension - Hyrule itself in Skyward Sword. The blood of the goddess that is passed down through Zelda's lineage, and the spirit of the hero inherited by each Link are eternally bound in conflict with the incarnations of the Demon King Demise's hatred.
Hyrule is a land that has faced several dangers over the course of its existence, and Link almost always saves the day, with Breath of the Wild's second of two Calamities making the fact that he didn't succeed a plot point. The reason for this is because the hero's spirit always awakens when the Hyrule Royal Family is in danger. This could be taken to assume that when each Link is born - or at least every Link that appears in the games - it's because he will be needed to protect Hyrule when the time rises for him to become a hero.
Although Link may not technically always have the same name due to the player having control over that, everything else about the prophecy checks out. The exploits of Hyrule's various heroes have been written in legends time and time again, establishing his pattern of fighting the evils of the land. Link has always been Zelda's hero, and he is one of the most important parts of Hyrule's history as a result.
The Hero's Spirit In The Legend Of Zelda Descended From An Ancient Hylian Bloodline
The hero's spirit has existed throughout Hyrule's history - just as long as most of the other myths that surround the region. While it ensures that there will always be a hero to save Hyrule, it also provides an explanation for why every version of Link seen thus far has been a Hylian. The inheritors of the hero's spirit are just as tied into the timeline of Hyrule as the lineage of the Hyrule Royal Family.
The spirit of the hero was born from the bloodline of the Knights of Hyrule. It does make sense that the heroes that continue to protect Hyrule would be descended from the legacy of those devoted to defending its royal family. The curse given after Demise's final boss battle in Skyward Sword illustrates how the spirit of the hero has likely been passed down through those with close ties to Hylian nobility. Since Zelda's lineage possesses the blood of the goddess, and its protectors have historically possessed the hero's spirit, their successors will continue their battles against Demise's incarnations.
Link has been a Hylian in every game not just because it allowed him to keep his usual design, but because his existence is defined by the series' lore. Even though Link himself has rarely been an official knight in Hyrule's service, with his incarnation in Breath of the Wild being one of the rare exceptions, the original knights were the source of what is now the hero's spirit. During Zelda's Hyrule Royal Family's long reign, the descendants of their knights have continued defending them and fighting against Demise's legacy, namely Ganon.
The Legend Of Zelda's Prophecy Does Not Mean That Link Will By Hylian Forever
Although every version of Link has been a Hylian thus far, there is always a chance that the next game could change that trend. While the original Knights of Hyrule were seemingly all Hylians, there is no guarantee that the same would be true for all of their descendants. There is plenty of reason to believe that a future incarnation of Link could be of a race other than Hylian.
Interracial marriages do exist in The Legend of Zelda's universe, and the player can even witness and Hylian and Gerudo marry in Breath of the Wild. It's possible that the hero's spirit could eventually be passed to a non-Hylian. After all, while Zelda has the blood of the goddess, the hero's spirit lives in her protectors, making its hosts more flexible. Zelda's alternate versions of Link have hinted that this could lead to something interesting.
For example, a Rito Link may use a bow as their signature weapon, since it is the preferred weapon of the Rito, or a Zora Link could see an adventure that largely takes place underwater with new mechanics. One of the most interesting possibilities could be a Gerudo Link, because not only would they likely be the first female Link in one of the main games, but it could also set up an interesting confrontation with the most infamous Gerudo and incarnation of Demise, Ganondorf.
Given how much time has passed since the founding of Hyrule, the bloodline of the hero's spirit could have spread throughout Hyrule. Any point where one of these descendants partnered with a non-Hylian opened the possibility for a non-Hylian Link sometime in the future. Players have already seen Zelda characters that would make excellent protagonists aside from Link, and a more unique version of Link could be yet another example.
Link has always appeared as a Hylian in The Legend of Zelda due to the hero's spirit that was passed down through the legacy of the Knights of Hyrule. While Link's look is a series tradition, it's not a guarantee that Zelda's protectors in the future will remain the same. Although Link has reincarnated as a Hylian throughout The Legend of Zelda, his next descendant may be able to change the series.
Source: Nintendo Unity/YouTube