In the future we will have more and more leisure as machine replaced many of the tasks we do at home and at work.what are the benefits this will bring and also the problems it will cause?

Well the benefits would be as you said "leisure" time to relax! Everyone's wanting... But the problems are that it will lead to idleness, a certain unwillingness to work and will cause obesity and other diseases as people won't get up or do any work which will lead to lack of calorie burning..