The outcome of the hornet attack depends on the amount of the attackers. If there's only few hornets attacking bees, they will loose.
No matter how many bees die, they'll begin covering hornets with their own bodies. Then the temperature begins rising around the hornet , and it will die sooner than bees due to the heat. Bees can stand higher temperatures than hornets.
But this works only when there's few hornets attacking. 30 of them may be too much for the bees nest of the size shown in the movie.
Harppa