I really don't want to say Wind Fish, although I would love to see him again in this capacity. The look and color does not match the wind fish at all.
First of all the wind fish is very colorful and decorated, while the servant in the trailer is mostly a brown color. Second the Wind fish seems to be based off of a blue whale. Which does not have a row of teeth, it has baleen plates in their place.
This is visible in all pics of the Wind Fish as well.
Now the creature in the trailer as I said earlier is a brown color and seems to have a very rough spiky outer skin. Which could just be fish scales.
The closest thing I have seen so far to match is Jabu Jabu which is a similar brownish color, has a row of teeth, and as seen in OoT people can enter the mouth and come out unharmed.
Any more details are hard to match up, since the creature has a longer hairlike thing on the top of it's head. Jabu Jabu wears a gold headdress so it cannot be confirmed in OoT. Jabun of WW had a single long feeler that held a lantern, but did not match many of the other descriptions.
Personally I do think it would be interesting if the servant was Jabu Jabu, since it might give us a better look at the actual character and purpose of the otherwise mindless fish that appeared in OoT.