If everyone becomes a vegan, won't this
create economic hardship for those who depend on animal
agriculture?
Yes, if everyone becomes a vegan, then many people who
depend on animal agriculture will have to find a new way to earn
a living.
Several hundred years ago, many people's jobs and economic well being depended on the continuation of the slave trade. Nevertheless, the ethics of the situation dictated that the slave trade should be abolished, even though this meant that these people would have to find a new way to earn a living.
There is nothing new or unusual about the process of an entire industry disappearing. For example, people who worked in the horse carriage industry needed to find new jobs after cars were invented.
Follow up questions:
If everyone becomes a vegan, then what will we do with all the farm animals?
Isn't it insulting to compare human beings with animals?