The Seven Dwarfs Mine Train at the Magic Kingdom has recently soft opened to guests.
A limited number of guests in the Fantasyland area have been able to ride the Seven Dwarfs Mine Train coaster during intermittent soft openings. There have been reports from guests who rode with varying wait times from walk-on to 20 minutes.
The ride will officially open on May 28th, although soft openings between now and then are increasingly likely. There has been unconfirmed speculation that the Mine Train will open for the Rock Your Disney Side 24 hour event taking place on Friday May 23.
As always with soft openings, the ride may open and close at any moment, and you may not be able to ride.