It's definitely possible, even likely, that we would reduce work hours entirely, the way you laid it out is pretty convincing. I think you are probably correct in that a 35 hour, or 30 hour week could easily work within a socialist economy while maintaining the base level of living standards (that is, everyone eats and can take part in recreation, but there are less treats). I'm not so sure about within a capitalist economy though, I think since capitalism requires ever increasing profit and growth, it requires an increase in productivity and stagnating wages to sustain itself. But we weren't originally talking about capitalist economy anyway.

I guess it's just hard to imagine a world where I work less while also actually working to solve real problems that need solving, not working for some capitalist company making widgets. And it's also hard to imagine that there wouldn't be an enormous amount of work that needs to be done. But we also have a lot of people.