What is the impact of Boxer's death?
For a while at the end of Chapter IX, it looks as if Boxer's death is going to have a huge impact. You sort of expect that the protest that erupts when he is taken away will end up making a difference. But then nothing happens for three days and then Squealer's explanation of his death smooths everything over. The rest of the animals either believe what Squealer says or (maybe) they are too afraid to go against the pigs.
At any rate, Boxer's death has no impact in the way you might think. It does not cause the animals to rise up. All that happens is that the pigs use Boxer as a hero to try to bolster their rule. They talk about how the animals should live by the same rules (hard work and reverence for Napoleon) that Boxer lived by.
So if Boxer's death has any impact at all, it is simply to help the pigs take even firmer control of the farm.