That seems to be a moving target, always about two months away. Until they pick a date and make an announcement I'm not going to believe any estimate.
At this point, it's not surprising. They've been working on Union Depot since 2009, but didn't come to an agreement with the host railroads to connect the station to rail until last April. Then Amtrak didn't sign on until November 2013, almost a year after the depot "opened." With the Ramsey County Board in charge, everything takes a long time, and it all has to be done sequentially. Apparently you can't negotiate with the railroads until you've finished the station.
I can certainly see why Amtrak wasn't interested in signing anything about moving to Union Depot until the County Board had gotten an agreement with the railroads. They seem just as happy at Midway, and will still attach and detach cars there even after moving passenger operations to Union Depot. Amtrak clearly wasn't a prime mover in the restoration.
I'll bet money that light rail is open to Union Station before the Empire Builder stops there. The Green Line
has to open before the All-Star Game in July. Union Depot has no such deadline.
So with this beautiful and awesome building coming back on line, how does that change the prospects for getting new services to say Chicago or Winnipeg, if any?
Not much. One reason for renovating Union Depot was that at the time there seemed a reasonable possibility of extra service to Chicago. That's not going to happen with the present Wisconsin state government. I don't think there's much interest in a Winnipeg line, though it's remarkably expensive to travel between the Twin Cities and Winnipeg. The proposed (and mostly dead in the water) service to Duluth would, I think, terminate at Target Field, not St. Paul Union Depot. The same is true, of course, for any trains to St. Cloud.