South Dakota supporters of top-two systems will try to qualify an initiative in 2018 for their system. See this story.
The story is erroneous when it says that Louisiana has a top-two system. Louisiana had a top-two system from 1975 through 1997, but after the Louisiana version of top-two was declared to violate federal law (in the US Supreme Court decision Foster v Love), Louisiana abolished primaries and only has general elections in November (for Congress) and a run-off in December if no one gets 50%. Thanks to Mike Drucker for this news.