I don't know-they have all the power in their hands. And it breaks my heart thinking of Tigress's reaction, because he is "closest thing to father she ever had" They killed Stoick-I see there is big chance for they to do Shifu the same.
But Stoick was rather minor, whilst Shiu is beloved to the utter by us fans. Plus it's a kids movie, and I bet killing Shifu would be too extreme, and possibly even psychologically damaging to kids, especially after he's been around so long, and so beloved.
I bet if they killed him, kids and adults in theaters worldwide would be bawling uncontrollably and angry parents would rage, try to sue, and even threaten Dreamworks.
Tigress would undeniably be crying hysterically with us fans, begging with us,"Why, why, WHYYYY???!!!"
We could make a petition for them to spare Shifu; it'd work out.