(SERIOUSLY: spoiler alert!)
... NOT Tigress! *phew*
The episode "Bride of Po" (*) makes it clear that Tigress does not have, nor has she ever had, any romantic feelings for Po. She considers him a friend and that's it. Tigress is simply very protective of her friends, and Po, in his very delusional mind, misinterpreted this as affection. Po actually thought Tigress had a crush on him! Hehe, how good of him to "let her down gently". *snicker*
Anyway.
I think the signal from Dreamworks is very clear: the TiPo-pairing will never happen. At least not officially, which is good enough for me. I am sure it won't stop fans from writing more ficto