Neill Blomkamp may be well on his way to becoming the only sci-fi writer-director who matters. And if “Elysium” is more an evolutionary leap than a revolutionary one from his break-out hit “District 9,” it still shows him in great form telling a story from the future ripped from today’s political hot-button issues. Blomkamp looked at his still racially divided native South Africa and concocted a tale of “Us vs.