Hah the polar bear wants to eat the killer whale. and he could if the whale was stuck. the polar bear would attack it and kill it by biting around its blowhole. And the killer whale wants to eat the polar bear and it would if the bear fell in.
As we melt our ice caps and the ice where these wonderful creatures live disappears, then polar bears will simply become extinct. The human race has much to answer for when it comes to how our actions effect the other creatures on the planet.