Communism when poverty isn't a possibility

A lot of the justification for communism seems to be based on the fact that the working classes have often been oppressed throughout history, working long hours but struggling to put food on the table. What if technology advances so that even those who don't work at all have sufficient food, shelter, healthcare, etc.? It doesn't seem like this would stop capitalism, because there would still be markets for luxury items. But would a guaranteed end to poverty make any of you change your support for communism? If not, what does communism achieve over a capitalist society that doesn't have poverty?