My friends and I are currently disagreeing over this. Though it seems intuitive that most people would no longer work, it's difficult to create an argument from a strictly philosophical perspective. Essentially, put the fact that working is a societal structure and that capitalism is inherently unfavorable towards workers. I guess it would be important to define what work even constitutes (would certain hobbies or activities not be seen as work?). The only thing I'm able to reason is that working is only instrumental for what we really want (recognition, not be bored, etc.).