False. Minnesota is not in play. Not for anytime soon.
Walter Mondale won Minnesota (his home state) by only a small plurality in 1984 and Al Gore won Minnesota by only a small plurality in 2000. It didn't mean that Minnesota was coming into play for the GOP. Minnesota is a Lean/Likely D state and that won't change for a while.
Many white-working class voters in the Iron Range of Minnesota has still (mostly) stuck by the Minnesota DFL Party and the national Democratic Party. It's the rural areas of MN that have turned away from the Democrats but that's being outweighed by the urban and suburban areas of MN. Also, rural areas of MN are declining in the population. Meanwhile, the urban and suburban areas are increasing in population.
Hillary was just uniquely disliked. Any major Democratic candidate in 2020 is going to do much better than Hillary did. Every Minnesota Democrat running statewide in 2018, besides Keith Ellison (he had a scandal hanging around him), won by a decent margin.