My personal opinion:
Winning over Union Bosses: Probability = 0%
Winning over Union Members: Trump must have already accomplished that to some extent in Election 2016. It would be nice if we had some data. In any case winning again in 2020 will require repeating his sweep of OH, PA, WI and MI or at least most of them. So he has to hang on to the 2016 converts and, if possible, expand their numbers.
The key to that is winning over union members (and their wives) and other working class folks particularly in the manufacturing sector. His job growth policies are clearly aimed at achieving that goal. On Day 1 he invites the mostly manufacturing CEOs and the Unions to the White House. On Day 1! The Dems will not fail to see the message that sends. The union guys and gals will also take notice. Trump is well on his way to stealing union members from the Dems in 2020 and hopefully beyond.
Keep in mind not much of the manufacturing sector workforce is unionized. This isn’t 1969.
They were going ape shits yesterday on Facebook about this.