Suffering is very serious. Death is very important. Let me instead talk about something else that is becoming both serious and important, as the world gets richer and more awesome: the problem of pleasure.
Excessive leisure time is a problem that has only become widespread in the past century. As non-human intelligences get more sophisticated, it may be the case that human work remains extremely important; however, it may also be that humans are faced with increasing leisure. If that is the case, the critical problem facing humanity will be how to enjoy ourselves. If that seems silly, consider your favorite dystopian images of the future: only humans who understand how to enjoy themselves can demand living conditions in which they are able to do so.