Coz there is only three possiblities here: Kili, Legolas and Thranduil.
PJ clearly says no romance between her and Legolas, but from the trailer, we could see Legolas did have some sort of feelings towards her, but she seems not to feel the same way towards him.
So, Kili or Thranduil?
from the preivous two trailers, not even a dame second showing something between Kili and Tauriel, not a second momenent, it seems nothing happened between them.
if there is something that happens in the movie which will release in December, it would violate the tradition of Hollywood as no signs can be tracked down.
However, shocking enough there is a lot of sences between Tranduil and Tauriel. and believe or not, we do see a lot when the king is even in his bedroom, it is way too intimate that implies something.