Being a longtime cetacean fan, I'm excited to see these scientists (and a philosopher) saying dolphins are smart enough to have some of the rights we accord to persons. All popular science article warnings apply, but there's a pretty good roundup of their cognitive abilities at the linked article.
Assuming that humans don't screw things up by killing ourselves or the dolphins, I think there'll be a time when humans can engage in much fuller communication with dolphins than currently possible. We'll probably need some really crazy neurotechnology to make this work out, but I think humans will eventually put that together given enough time. When it happens, it'll be one of the coolest things our species has ever done.