If Skyward Sword is at the beginning of the timeline, there is no possibility of there being Koroks in the game. The Koroks came into existence during the Great Flood (WW) when the Kokiri "evolved" into the Koroks. How they did that I will never know, but since the Great Flood happened AFTER Ocarina of Time, and Skyward Sword is going to happen BEFORE Ocarina of Time, the Koroks will more then likely not make an appearance.
However, I can see how you could mistake that creature for a Korok. Here are some pictures for comparison:
This creature does look a bit similar to the Koroks colorwise and sizewise. When I first saw this creature, I thought that it looked like a badger/raccoon/beaver/bird/platypus thing. It is obviously a new race or animal. I don't know this creature's significance in the game yet, but I do think that he could be used as part of a sidequest. It seems as though you meet him at the beginning of the game considering the sword and shield that Link is using. They look like beginner's weapons, and the symbol on Link's shield looks like something you would find in Skyloft.